Add GitHub Actions CI workflow

Runs on every push/PR to main:
- Matcher unit tests via pytest (Python 3.11)
- Docker build check for frontend, matcher, and dashboard

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

.github/workflows/ci.yml

@@ -0,0 +1,59 @@
+name: CI
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  test:
+    name: Matcher Unit Tests
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Python 3.11
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+          cache: pip
+
+      - name: Install dependencies
+        run: |
+          pip install -r matcher/requirements.txt
+          pip install pytest
+
+      - name: Run tests
+        run: pytest matcher/test_matcher.py -v
+
+  docker-build:
+    name: Docker Build Check
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Build frontend
+        uses: docker/build-push-action@v6
+        with:
+          context: ./frontend
+          push: false
+
+      - name: Build matcher
+        uses: docker/build-push-action@v6
+        with:
+          context: ./matcher
+          push: false
+
+      - name: Build dashboard
+        uses: docker/build-push-action@v6
+        with:
+          context: ./dashboard
+          push: false