chore: Add initial workflows, licence and docs

.github/CODEOWNERS

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+# The CODEOWNERS file defines individuals or teams that are
+# responsible for code this repository.
+
+# Code owners are automatically requested for review when someone opens a
+# pull request that modifies code that they own.
+# Code owners are not automatically requested to review draft pull requests
+# Each line is a file pattern followed by one or more owners.
+
+# These owners will be the default owners for everything in the repo.
+# Unless a later match takes precedence, @krusche and @jpbernius will be
+# requested for review when someone opens a pull request.
+
+*    @ls1intum/github-action-ui

.github/PULL_REQUEST_TEMPLATE.md

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+<!-- Thanks for contributing to Helios! Before you submit your pull request, please make sure to check all tasks by putting an x in the [ ] (don't: [x ], [ x], do: [x]). Remove not applicable tasks and do not leave them unchecked -->
+<!-- If your pull request is not ready for review yet, create a draft pull request! -->
+
+### Motivation
+<!-- Why is this change required? What problem does it solve? -->
+<!-- If it fixes an open issue, please link to the issue here. -->
+
+
+### Description
+<!-- Describe your changes in detail -->
+
+### Testing Instructions
+<!-- Please describe in detail how reviewers can test your changes. Make sure to take all related features and views into account! -->
+#### Prerequisites:
+- GitHub Account without having any additional access-rights (e.g. admin, owner)
+- ...
+#### Flow:
+1. Log in to Helios as a Developer
+2. Navigate to Settings
+3. ...
+
+### Screenshots
+<!-- Add screenshots to demonstrate the changes in the UI. Remove the section if you did not change the UI. -->
+
+### Checklist
+<!-- Remove tasks that are not applicable for your PR. Please only put the PR into ready for review, if all relevant tasks are checked! -->
+#### General
+- [ ] PR description explains the purpose and changes. [(f.e. following the 'Conventional Commits')](https://www.conventionalcommits.org/en/v1.0.0/)
+- [ ] Changes have been tested locally.
+- [ ] Screenshots have been attached.
+
+#### Server
+- [ ] Code is performant and follows best practices
+- [ ] I documented the Java code using JavaDoc style.
+
+#### Client
+- [ ] I documented the TypeScript code using JSDoc style.
+- [ ] I added multiple screenshots/screencasts of my UI changes.
+- [ ] I translated all newly inserted strings into English and German.

.github/labeler.yml

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+server:
+  - changed-files:
+      - any-glob-to-any-file: server/**
+
+client:
+  - changed-files:
+      - any-glob-to-any-file: client/**
+
+documentation:
+  - changed-files:
+      - any-glob-to-any-file: docs/**
+
+feature:
+  - head-branch: ['^feature', '^feat']
+
+bug:
+  - head-branch: ['^fix', '^bug']

.github/workflows/docs.yml

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+name: Documentation
+
+on:
+  pull_request:
+    paths:
+      - 'docs/**'
+      - '.github/workflows/docs.yml'
+  push:
+    branches:
+      - main
+    paths:
+      - 'docs/**'
+      - '.github/workflows/docs.yml'
+
+# Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+jobs:
+  docs:
+    runs-on: ubuntu-22.04
+    steps:
+      - uses: actions/checkout@v4
+      - uses: FelixTJDietrich/sphinx-action@java
+        with:
+          docs-folder: "docs/"
+          build-command: make html dirhtml
+      - uses: actions/upload-artifact@v4
+        with:
+          name: Documentation
+          path: docs/_build/html/
+      - uses: actions/upload-pages-artifact@v3
+        with:
+          path: docs/_build/dirhtml/
+  deploy:
+    if: github.ref == 'refs/heads/main'
+    environment:
+      name: github-pages
+      url: "https://ls1intum.github.io/Helios/"
+    runs-on: ubuntu-22.04
+    needs: docs
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4

.github/workflows/pr-labeler.yml

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+name: "Pull Request Labeler"
+on:
+  pull_request_target:
+
+jobs:
+  labeler:
+    name: "Apply labels"
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      pull-requests: write
+    steps:
+      - name: "Checkout repository"
+        uses: actions/checkout@v4
+
+      - uses: actions/labeler@v5
+        with:
+          configuration-path: .github/labeler.yml
+          sync-labels: true
+
+      - name: "Apply size label"
+        uses: actions/github-script@v7
+        with:
+          script: |
+            console.log("Fetching pull request diff...");
+            const diff = await github.rest.pulls.get({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              pull_number: context.issue.number,
+              mediaType: {
+                format: "diff",
+              },
+            });
+            console.log("Pull request diff fetched successfully.");
+
+            const changedLines = diff.data
+              .split("\n")
+              .filter(line => line.startsWith('+') || line.startsWith('-'))
+              .length;
+            console.log(`Number of changed lines: ${changedLines}`);
+
+            let label = '';
+            if (changedLines > 1000) label = 'size:XXL';
+            else if (changedLines > 499) label = 'size:XL';
+            else if (changedLines > 99) label = 'size:L';
+            else if (changedLines > 29) label = 'size:M';
+            else if (changedLines > 9) label = 'size:S';
+            else label = 'size:XS';
+
+            console.log("Fetching existing labels...");
+            const labels = await github.rest.issues.listLabelsOnIssue({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.issue.number,
+            });
+
+            const sizeLabels = labels.data
+              .filter(label => label.name.startsWith('size:'))
+              .map(label => label.name);
+
+            const removeLabels = sizeLabels.filter(sizeLabel => sizeLabel !== label);
+            if (removeLabels.length > 0) {
+              console.log(`Removing existing size labels: ${removeLabels.join(', ')}`);
+              for (const label of removeLabels) {
+                await github.rest.issues.removeLabel({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  issue_number: context.issue.number,
+                  name: label,
+                });
+              }
+              console.log("Existing size labels removed.");
+            } else {
+              console.log("No size labels to remove.");
+            }
+
+            if (label) {
+              if (sizeLabels.includes(label)) {
+                console.log(`Label "${label}" already applied.`);
+              } else {
+                console.log(`Applying label "${label}" to the pull request...`);
+                await github.rest.issues.addLabels({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  issue_number: context.issue.number,
+                  labels: [label]
+                });
+                console.log(`Label "${label}" applied successfully.`);
+              }
+            } else {
+              console.log("No label to apply.");
+            }

.github/workflows/pullrequest-opened.yml

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+name: Pull Request Opened
+on:
+  pull_request_target:
+    types: [opened]
+
+jobs:
+  assign:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Assign Pull Request to its Author
+        uses: technote-space/assign-author@v1

.github/workflows/pullrequest-readyforreview.yml

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+name: Pull Request Ready for Review
+on:
+  pull_request_target:
+    types: [ready_for_review]
+
+jobs:
+  pullRequestReadyForReview:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Label "ready for review"
+        uses: actions/github-script@v7
+        with:
+          github-token: ${{secrets.GITHUB_TOKEN}}
+          script: |
+            await github.rest.issues.addLabels({
+              issue_number: context.issue.number,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              labels: ['ready for review']
+            })

.github/workflows/pullrequest-stale.yml

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+name: Stale
+on:
+  schedule:
+    - cron: "0 12 * * *"
+
+jobs:
+  stale:
+    if: github.repository_owner == 'ls1intum'
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check for stale PRs
+        uses: actions/stale@v9
+        with:
+          days-before-stale: 7
+          days-before-close: 14
+          # Disable issue checking, only PR
+          days-before-issue-stale: -1
+          remove-stale-when-updated: true
+          stale-pr-label: "stale"
+          exempt-pr-labels: "no-stale"
+          labels-to-remove-when-stale: "ready for review"
+          stale-pr-message: >
+            There hasn't been any activity on this pull request recently. 
+            Therefore, this pull request has been automatically marked as stale
+            and will be closed if no further activity occurs within **seven** days.
+            Thank you for your contributions.