feat: add base template with Pico CSS dark theme and home page

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

tests/test_pages.py

@@ -0,0 +1,22 @@
+"""Tests for HTML page routes."""
+
+from fastapi.testclient import TestClient
+
+
+class TestHomePage:
+    """Tests for GET /."""
+
+    def test_home_returns_200(self, client: TestClient) -> None:
+        """GET / should return HTTP 200."""
+        response = client.get("/")
+        assert response.status_code == 200
+
+    def test_home_contains_app_name(self, client: TestClient) -> None:
+        """GET / should render HTML containing the app name."""
+        response = client.get("/")
+        assert "SneakySwole" in response.text
+
+    def test_home_has_dark_theme(self, client: TestClient) -> None:
+        """GET / should use the dark theme."""
+        response = client.get("/")
+        assert 'data-theme="dark"' in response.text