F4: no Alembic migrations; bootstrap always uses the fallback schema #84

Found in ART Milestone 0 (#53).

Problem

api/db.py:bootstrap() runs Alembic only if alembic.ini exists. It does not exist, so every startup takes _bootstrap_fallback_schema() (db.py:165-172, which logs a warning). The fallback is CREATE TABLE IF NOT EXISTS, so schema changes never reach an existing database. The ART work (ADR-0002, ADR-0003) adds many tables and constraints, so versioned migrations are a prerequisite.

Fix

Add alembic.ini and an alembic/ directory with a baseline revision matching the current fallback schema. Then add a migration up/down test in CI.

Part of ART M1.

Generated by Claude Code