Add security ownership, dependency maintenance, and CodeQL

.github/CODEOWNERS

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+# Enforce code-owner review in the default branch ruleset for these requests
+# to become a merge requirement. Restrict broad ruleset bypasses separately.
+/.github/ @reddit/devplatform
+/.nvmrc @reddit/devplatform
+/.yarn/ @reddit/devplatform
+/.yarnrc.yml @reddit/devplatform
+/package.json @reddit/devplatform
+/yarn.lock @reddit/devplatform
+/docusaurus.config.ts @reddit/devplatform
+/plugins/ @reddit/devplatform
+/scripts/ @reddit/devplatform

.github/dependabot.yml

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+version: 2
+updates:
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 5
+    groups:
+      action-maintenance:
+        patterns:
+          - "*"
+        update-types:
+          - minor
+          - patch
+
+  - package-ecosystem: npm
+    directory: /
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 10
+    groups:
+      docusaurus-maintenance:
+        patterns:
+          - "@docusaurus/*"
+        update-types:
+          - minor
+          - patch

.github/workflows/codeql.yml

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+name: CodeQL Security
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+  schedule:
+    - cron: "17 6 * * 1"
+
+permissions: {}
+
+jobs:
+  analyze:
+    name: Analyze ${{ matrix.language }}
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    permissions:
+      contents: read
+      security-events: write
+    strategy:
+      fail-fast: false
+      matrix:
+        language: [actions, javascript-typescript]
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
+        with:
+          persist-credentials: false
+
+      # These languages require no application build or dependency installation.
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@9b3254085494b55a0f7c4c2b3d2d52cc712ce370 # v4
+        with:
+          languages: ${{ matrix.language }}
+          build-mode: none
+
+      - name: Analyze code
+        uses: github/codeql-action/analyze@9b3254085494b55a0f7c4c2b3d2d52cc712ce370 # v4
+        with:
+          category: /language:${{ matrix.language }}