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>

Dockerfile

@@ -9,6 +9,8 @@ RUN pip install --no-cache-dir -r requirements.txt
 
 COPY app/ .
 
+RUN mkdir -p /data
+
 EXPOSE 5199
 
 CMD ["python", "-u", "main.py"]