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>

.gitignore

@@ -1,6 +1,10 @@
 # Environment file with real secrets - NEVER commit this
 .env
 
+# Virtual environments
+.venv/
+venv/
+
 # Python
 __pycache__/
 *.py[cod]
@@ -12,9 +16,17 @@ dist/
 build/
 *.egg
 
+# Database
+*.db
+*.db-wal
+*.db-shm
+
 # Docker
 *.log
 
+# Test / cache
+.pytest_cache/
+
 # Editor
 .vscode/
 .idea/