ci: add labeler action

.github/labeler.yml

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+# Bitcoin Finality Governor (BFG)
+'area: bfg':
+  - changed-files:
+      - any-glob-to-any-file:
+          - "api/bfgapi/**"
+          - "cmd/bfgd/**"
+          - "database/bfgd/**"
+          - "docker/bfgd/**"
+          - "service/bfg/**"
+
+# Bitcoin Secure Sequencer (BSS)
+'area: bss':
+  - changed-files:
+      - any-glob-to-any-file:
+          - "api/bssapi/**"
+          - "cmd/bssd/**"
+          - "docker/bssd/**"
+          - "service/bss/**"
+
+# GitHub Actions workflows (CI)
+'area: ci':
+  - changed-files:
+      - any-glob-to-any-file:
+          - ".github/workflows/**"
+
+# Deucalion (Prometheus service)
+'area: deucalion':
+  - changed-files:
+      - any-glob-to-any-file:
+          - "service/deucalion/**"
+
+# Docker images
+'area: docker':
+  - changed-files:
+      - any-glob-to-any-file:
+          - "docker/**"
+
+# hemictl
+'area: hemictl':
+  - changed-files:
+      - any-glob-to-any-file:
+          - "cmd/hemictl/**"
+
+# @hemilabs/pop-miner NPM package
+'area: @hemilabs/pop-miner':
+  - changed-files:
+      - any-glob-to-any-file:
+          - "web/packages/pop-miner/**"
+
+# Makefiles
+'area: make':
+  - changed-files:
+      - any-glob-to-any-file: "**/Makefile"
+
+# WebAssembly PoP Miner
+'area: popm/wasm':
+  - changed-files:
+      - any-glob-to-any-file:
+          - "web/popminer/**"
+
+# PoP Miner
+'area: popm':
+  - changed-files:
+      - any-glob-to-any-file:
+          - "cmd/popmd/**"
+          - "docker/popmd/**"
+          - "service/popm/**"
+
+# Tiny Bitcoin Daemon (TBC)
+'area: tbc':
+  - changed-files:
+      - any-glob-to-any-file:
+          - "api/tbcapi/**"
+          - "cmd/tbcd/**"
+          - "database/tbcd/**"
+          - "service/tbc/**"

.github/workflows/labeler.yml

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+# GitHub Actions workflow to automatically label pull requests.
+name: "Label"
+on: [ "pull_request_target" ]
+
+jobs:
+  labeler:
+    name: "Pull Request"
+    runs-on: "ubuntu-latest"
+    permissions:
+      contents: read
+      pull-requests: write
+    steps:
+      - name: "Label pull requests"
+        uses: actions/labeler@v5