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_static.py

@@ -0,0 +1,85 @@
+# ABOUTME: Tests for static file serving with cache headers.
+# ABOUTME: Verifies /static/v1/ path and immutable cache-control.
+
+import os
+
+import pytest
+
+
+def make_test_settings(
+    csrf_secret: str = "test-secret",
+    trusted_proxy_ips: str = "127.0.0.1",
+):
+    """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
+        return Settings()
+    finally:
+        os.environ.clear()
+        os.environ.update(old_env)
+
+
+class TestStaticFileServing:
+    """Tests for static file serving."""
+
+    @pytest.fixture
+    def static_dir(self, tmp_path):
+        """Create a temporary static directory with test files."""
+        static_v1 = tmp_path / "static" / "v1"
+        static_v1.mkdir(parents=True)
+
+        # Create a test CSS file
+        test_css = static_v1 / "test.css"
+        test_css.write_text("body { color: red; }")
+
+        # Create a test JS file
+        test_js = static_v1 / "test.js"
+        test_js.write_text("console.log('test');")
+
+        return tmp_path / "static"
+
+    @pytest.fixture
+    def client(self, seeded_db, static_dir):
+        """Create a test client with static file serving configured."""
+        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,
+            static_dir=static_dir,
+        )
+        return TestClient(app, raise_server_exceptions=False)
+
+    def test_static_files_are_served(self, client):
+        """Static files under /static/v1/ are accessible."""
+        resp = client.get("/static/v1/test.css")
+        assert resp.status_code == 200
+        assert "body { color: red; }" in resp.text
+
+    def test_static_files_have_immutable_cache_headers(self, client):
+        """Static files have Cache-Control: immutable header."""
+        resp = client.get("/static/v1/test.css")
+        assert resp.status_code == 200
+
+        cache_control = resp.headers.get("cache-control", "")
+        assert "immutable" in cache_control
+        assert "max-age=31536000" in cache_control
+        assert "public" in cache_control
+
+    def test_static_js_files_served(self, client):
+        """JavaScript files are served correctly."""
+        resp = client.get("/static/v1/test.js")
+        assert resp.status_code == 200
+        assert "console.log" in resp.text
+
+    def test_static_404_for_missing_files(self, client):
+        """Missing static files return 404."""
+        resp = client.get("/static/v1/nonexistent.css")
+        assert resp.status_code == 404