feat: Integrate Playwright into docker-compose

Adds Playwright service to docker-compose.yml for easier test execution
and better integration with existing database services.

## Changes

- Add `playwright` service to docker-compose.yml:
  - Uses official Playwright image (mcr.microsoft.com/playwright:v1.49.1-noble)
  - Runs as non-root user (pwuser) for security
  - Uses host networking to access dev server on localhost:3000
  - Loads environment variables from .env
  - Uses `profiles: [test]` to keep it optional
  - Mounts node_modules volume to prevent permission issues

- Update documentation in AGENTS.md:
  - Replace standalone Docker commands with docker-compose usage
  - Document two usage patterns: `docker compose run` and `--profile test`
  - Explain benefits of integrated setup

## Usage

```bash
# Start database services
docker compose up -d

# Start dev server
pnpm dev

# Run Playwright tests in Docker
docker compose run --rm playwright
```

Or with profiles:

```bash
# Run tests one-off
docker compose --profile test run --rm playwright
```

## Benefits

- Unified infrastructure setup (database + tests)
- No need for separate Dockerfile build step
- Easier for new developers to run tests
- Consistent with existing docker-compose workflow

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

docker-compose.yml

@@ -32,3 +32,26 @@ services:
       - "8080:8080"
     depends_on:
       - surrealdb
+
+  playwright:
+    image: mcr.microsoft.com/playwright:v1.49.1-noble
+    working_dir: /home/pwuser/app
+    user: pwuser
+    network_mode: host
+    volumes:
+      - .:/home/pwuser/app
+      - /home/pwuser/app/node_modules
+    environment:
+      - TEST_BLUESKY_HANDLE=${TEST_BLUESKY_HANDLE}
+      - TEST_BLUESKY_PASSWORD=${TEST_BLUESKY_PASSWORD}
+      - PLAYWRIGHT_BASE_URL=${PLAYWRIGHT_BASE_URL:-http://localhost:3000}
+    command: >
+      sh -c "
+        npm install -g pnpm &&
+        pnpm install --frozen-lockfile &&
+        npx playwright test
+      "
+    depends_on:
+      - surrealdb
+    profiles:
+      - test