Add fuzzy name search (pg_trgm) and living-person protection

Fuzzy search: pg_trgm extension + trigram GIN indexes on name parts and a GET /trees/{id}/persons?q= search ranked by trigram similarity (finds Mueller for 'muller'), privacy-filtered. Living-person protection: the privacy engine now derives possibly-living status (explicit flag, else no death fact + birth within ~100y or unknown) and returns 'redacted' for non-members of public/unlisted trees; the service minimises those records ('Living person', no vitals). Members are unaffected. 31 tests pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Justin Paul <justin@jpaul.me>

backend/tests/conftest.py

@@ -11,6 +11,7 @@ import os
 import pytest
 import pytest_asyncio
 from httpx import ASGITransport, AsyncClient
+from sqlalchemy import text
 from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
 
 import app.models  # noqa: F401 — register all models on Base.metadata
@@ -72,6 +73,7 @@ async def client():
 
     engine = create_async_engine(TEST_DATABASE_URL)
     async with engine.begin() as conn:
+        await conn.execute(text("CREATE EXTENSION IF NOT EXISTS pg_trgm"))
         await conn.run_sync(Base.metadata.drop_all)
         await conn.run_sync(Base.metadata.create_all)