docs: add comprehensive K6 load testing guide with API structure

- Document all API endpoints (auth, listings, payments, search)
- Include DTOs and request/response body shapes
- Document authentication methods and rate limits
- Provide database and environment configuration
- Include existing test setup (Playwright, Vitest)
- Detail CI/CD pipeline structure
- Recommend K6 endpoints and test patterns
- Provide file location references for quick lookup

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/codeql.yml

@@ -0,0 +1,61 @@
+name: CodeQL Analysis
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+  schedule:
+    # Run weekly on Monday at 06:17 UTC — off-peak to avoid :00/:30 congestion
+    - cron: "17 6 * * 1"
+
+concurrency:
+  group: codeql-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  actions: read
+  contents: read
+  security-events: write
+
+jobs:
+  analyze:
+    name: CodeQL (${{ matrix.language }})
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+
+    strategy:
+      fail-fast: false
+      matrix:
+        language: [javascript-typescript]
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@v3
+        with:
+          languages: ${{ matrix.language }}
+          # Use extended security queries for deeper analysis
+          queries: security-extended,security-and-quality
+          config: |
+            paths:
+              - apps/
+              - libs/
+            paths-ignore:
+              - node_modules/
+              - "**/dist/"
+              - "**/*.spec.ts"
+              - "**/*.test.ts"
+              - "**/__tests__/"
+
+      - name: Autobuild
+        uses: github/codeql-action/autobuild@v3
+
+      - name: Perform CodeQL Analysis
+        uses: github/codeql-action/analyze@v3
+        with:
+          category: "/language:${{ matrix.language }}"
+          # SARIF results are automatically uploaded to GitHub Security tab
+          upload: always