feat: add migration framework with FastMigrate integration

- Add migrations.py with create_migration, run_migrations, get_db_version
- Implement CLI migrate and create-migration commands
- Use FastMigrate's sequential 0001-*.sql naming convention
- Add comprehensive unit, integration, and E2E tests (35 tests)
- Add fresh_db_path and temp_migrations_dir test fixtures

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

PLAN.md

@@ -24,11 +24,11 @@ Check off items as completed. Each phase builds on the previous.
 - [x] **Commit checkpoint** (d8910d6)
 
 ### Step 1.3: Migration Framework
-- [ ] Create `migrations.py` using FastMigrate patterns
-- [ ] Create `cli.py` with `migrate` and `create-migration` commands
-- [ ] Create initial migration for `schema_migrations` table
-- [ ] Write tests for migration discovery and application
-- [ ] **Commit checkpoint**
+- [x] Create `migrations.py` using FastMigrate patterns
+- [x] Create `cli.py` with `migrate` and `create-migration` commands
+- [x] Create initial migration for `schema_migrations` table
+- [x] Write tests for migration discovery and application
+- [x] **Commit checkpoint**
 
 ### Step 1.4: Reference Tables Schema
 - [ ] Create migration for species, locations, products, feed_types, users tables