feat: add health endpoints, static serving, and base template (Step 7.2)

- Add /healthz endpoint with DB writable check
- Add /metrics endpoint with Prometheus-compatible format (enabled by default)
- Configure static file serving at /static/v1/... with immutable cache headers
- Create base page template with MonsterUI slate theme
- Create industrial farm aesthetic bottom navigation with custom SVG icons
- Add StaticCacheMiddleware for adding cache-control headers

Changes:
- src/animaltrack/web/routes/health.py: Health and metrics endpoints
- src/animaltrack/web/templates/: Base template, nav, and icons
- src/animaltrack/web/app.py: Integrate theme, routes, static serving
- src/animaltrack/config.py: metrics_enabled defaults to True

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/test_web_health.py

@@ -0,0 +1,129 @@
+# ABOUTME: Tests for health and metrics endpoints.
+# ABOUTME: Covers /healthz DB check and /metrics Prometheus format.
+
+import os
+from unittest.mock import MagicMock
+
+import pytest
+
+
+def make_test_settings(
+    csrf_secret: str = "test-secret",
+    trusted_proxy_ips: str = "127.0.0.1",
+    metrics_enabled: bool = True,
+):
+    """Create Settings for testing by setting env vars temporarily."""
+    from animaltrack.config import Settings
+
+    old_env = os.environ.copy()
+    try:
+        os.environ["CSRF_SECRET"] = csrf_secret
+        os.environ["TRUSTED_PROXY_IPS"] = trusted_proxy_ips
+        os.environ["METRICS_ENABLED"] = str(metrics_enabled).lower()
+        return Settings()
+    finally:
+        os.environ.clear()
+        os.environ.update(old_env)
+
+
+class TestHealthzEndpoint:
+    """Tests for /healthz endpoint."""
+
+    @pytest.fixture
+    def client(self, seeded_db):
+        """Create a test client for the app."""
+        from starlette.testclient import TestClient
+
+        from animaltrack.web.app import create_app
+
+        settings = make_test_settings(trusted_proxy_ips="testclient")
+        app, rt = create_app(settings=settings, db=seeded_db)
+        return TestClient(app, raise_server_exceptions=False)
+
+    def test_healthz_returns_200_when_db_healthy(self, client):
+        """GET /healthz returns 200 OK when database is healthy."""
+        resp = client.get("/healthz")
+        assert resp.status_code == 200
+        assert resp.text == "OK"
+
+    def test_healthz_returns_503_when_db_fails(self, seeded_db):
+        """GET /healthz returns 503 when database query fails."""
+        from starlette.testclient import TestClient
+
+        from animaltrack.web.app import create_app
+
+        # Create a mock db that raises on execute
+        mock_db = MagicMock()
+        mock_db.execute.side_effect = Exception("Database connection lost")
+
+        settings = make_test_settings(trusted_proxy_ips="testclient")
+        app, rt = create_app(settings=settings, db=mock_db)
+        client = TestClient(app, raise_server_exceptions=False)
+
+        resp = client.get("/healthz")
+        assert resp.status_code == 503
+        assert "Database error" in resp.text
+
+
+class TestMetricsEndpoint:
+    """Tests for /metrics Prometheus endpoint."""
+
+    @pytest.fixture
+    def client_metrics_enabled(self, seeded_db):
+        """Create a test client with metrics enabled."""
+        from starlette.testclient import TestClient
+
+        from animaltrack.web.app import create_app
+
+        settings = make_test_settings(
+            trusted_proxy_ips="testclient",
+            metrics_enabled=True,
+        )
+        app, rt = create_app(settings=settings, db=seeded_db)
+        return TestClient(app, raise_server_exceptions=False)
+
+    @pytest.fixture
+    def client_metrics_disabled(self, seeded_db):
+        """Create a test client with metrics disabled."""
+        from starlette.testclient import TestClient
+
+        from animaltrack.web.app import create_app
+
+        settings = make_test_settings(
+            trusted_proxy_ips="testclient",
+            metrics_enabled=False,
+        )
+        app, rt = create_app(settings=settings, db=seeded_db)
+        return TestClient(app, raise_server_exceptions=False)
+
+    def test_metrics_returns_200_when_enabled(self, client_metrics_enabled):
+        """GET /metrics returns 200 when metrics_enabled=True."""
+        resp = client_metrics_enabled.get("/metrics")
+        assert resp.status_code == 200
+
+    def test_metrics_returns_404_when_disabled(self, client_metrics_disabled):
+        """GET /metrics returns 404 when metrics_enabled=False."""
+        resp = client_metrics_disabled.get("/metrics")
+        assert resp.status_code == 404
+
+    def test_metrics_returns_prometheus_format(self, client_metrics_enabled):
+        """GET /metrics returns valid Prometheus text format."""
+        resp = client_metrics_enabled.get("/metrics")
+
+        # Check Content-Type
+        content_type = resp.headers.get("content-type", "")
+        assert "text/plain" in content_type
+
+        # Check body contains Prometheus format elements
+        body = resp.text
+        assert "# HELP" in body
+        assert "# TYPE" in body
+        assert "animaltrack_up" in body
+
+    def test_metrics_includes_db_health_metric(self, client_metrics_enabled):
+        """GET /metrics includes database health gauge."""
+        resp = client_metrics_enabled.get("/metrics")
+        body = resp.text
+
+        assert "animaltrack_db_healthy" in body
+        assert "# TYPE animaltrack_db_healthy gauge" in body