Implement automatic database migration system

Following design in ADR-020, implementation guidance, and quick reference.

Phase 1: Migration System Core (starpunk/migrations.py)
- Create migration runner with fresh database detection
- Implement is_schema_current() heuristic for fresh DB detection
- Add helper functions (table_exists, column_exists, index_exists)
- Complete error handling with MigrationError exception
- 315 lines of production code

Phase 2: Database Integration (starpunk/database.py)
- Modify init_db() to call run_migrations()
- Add logger parameter handling
- 5 lines changed for integration

Phase 3: Comprehensive Testing (tests/test_migrations.py)
- 26 tests covering all scenarios (100% pass rate)
- Tests for fresh DB, legacy DB, helpers, error handling
- Integration test with actual migration file
- 560 lines of test code

Phase 4: Version and Documentation
- Bump version to 0.9.0 (MINOR increment per versioning strategy)
- Update CHANGELOG.md with comprehensive v0.9.0 entry
- Create implementation report documenting all details

Features:
- Fresh database detection prevents unnecessary migrations
- Legacy database detection applies pending migrations automatically
- Migration tracking table records all applied migrations
- Idempotent execution safe for multiple runs
- Fail-safe: app won't start if migrations fail
- Container deployments now fully automatic

Testing:
- All 26 migration tests passing (100%)
- Fresh database scenario verified (auto-skip)
- Legacy database scenario verified (migrations applied)
- Idempotent behavior confirmed

Documentation:
- Implementation report in docs/reports/
- CHANGELOG.md updated with v0.9.0 entry
- All architecture decisions from ADR-020 implemented

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

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

starpunk/database.py

@@ -69,29 +69,38 @@ CREATE INDEX IF NOT EXISTS idx_auth_state_expires ON auth_state(expires_at);
 
 def init_db(app=None):
     """
-    Initialize database schema
+    Initialize database schema and run migrations
 
     Args:
         app: Flask application instance (optional, for config access)
     """
     if app:
         db_path = app.config["DATABASE_PATH"]
+        logger = app.logger
     else:
         # Fallback to default path
         db_path = Path("./data/starpunk.db")
+        logger = None
 
     # Ensure parent directory exists
     db_path.parent.mkdir(parents=True, exist_ok=True)
 
-    # Create database and schema
+    # Create database and initial schema
     conn = sqlite3.connect(db_path)
     try:
         conn.executescript(SCHEMA_SQL)
         conn.commit()
-        print(f"Database initialized: {db_path}")
+        if logger:
+            logger.info(f"Database initialized: {db_path}")
+        else:
+            print(f"Database initialized: {db_path}")
     finally:
         conn.close()
 
+    # Run migrations
+    from starpunk.migrations import run_migrations
+    run_migrations(db_path, logger=logger)
+
 
 def get_db(app):
     """