ci: Tier 1 OSS security scanners

CodeQL (security-extended for JS/TS) + Dependabot (npm + actions) +
OSV-Scanner. 100% free for public repos.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: claude

.github/dependabot.yml

@@ -0,0 +1,31 @@
+version: 2
+updates:
+  - package-ecosystem: npm
+    directory: "/"
+    schedule:
+      interval: weekly
+      day: monday
+      time: "06:00"
+      timezone: Etc/UTC
+    open-pull-requests-limit: 5
+    groups:
+      npm-security:
+        applies-to: security-updates
+        patterns:
+          - "*"
+      npm-minor-patch:
+        applies-to: version-updates
+        update-types:
+          - minor
+          - patch
+
+  - package-ecosystem: github-actions
+    directory: "/"
+    schedule:
+      interval: weekly
+      day: monday
+    open-pull-requests-limit: 3
+    groups:
+      actions:
+        patterns:
+          - "*"

.github/workflows/codeql.yml

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+name: CodeQL
+
+on:
+  push:
+    branches: [master, main]
+  pull_request:
+    branches: [master, main]
+  schedule:
+    - cron: '17 6 * * 1'
+
+permissions:
+  actions: read
+  contents: read
+  security-events: write
+
+jobs:
+  analyze:
+    name: Analyze (JS/TS)
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    steps:
+      - uses: actions/checkout@v4
+      - uses: github/codeql-action/init@v3
+        with:
+          languages: javascript-typescript
+          queries: security-extended
+      - uses: github/codeql-action/autobuild@v3
+      - uses: github/codeql-action/analyze@v3
+        with:
+          category: "/language:javascript-typescript"

.github/workflows/osv-scanner.yml

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+name: OSV-Scanner
+
+on:
+  push:
+    branches: [master, main]
+  pull_request:
+    branches: [master, main]
+  schedule:
+    - cron: '0 6 * * *'
+
+permissions:
+  actions: read
+  contents: read
+  security-events: write
+
+jobs:
+  scan:
+    uses: google/osv-scanner-action/.github/workflows/osv-scanner-reusable.yml@v2.0.1
+    permissions:
+      actions: read
+      contents: read
+      security-events: write