feat: scaffold v2 with FastAPI, SQLite database, and project structure

Migrate from raw HTTPServer to FastAPI, add SQLite database with schema
for known objects, embeddings, events, and settings. Add centralized
config, Pydantic models, and 22 database integration tests.

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

tests/conftest.py

@@ -0,0 +1,16 @@
+"""Shared fixtures for frigate-notify tests."""
+
+import os
+import sys
+import tempfile
+
+import pytest
+
+# Add app/ to sys.path so test modules can import application code
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), "..", "app"))
+
+
+@pytest.fixture
+def db_path(tmp_path):
+    """Provide a temporary database path for testing."""
+    return str(tmp_path / "test-frigate-notify.db")