fix: migration runner continues on failure instead of aborting

Previously, a single failed migration would abort all subsequent
migrations via raise RuntimeError. Now the runner logs the failure
and continues with remaining migrations, so independent schema
changes (e.g. 050-053) are not blocked by an unrelated failure
in an earlier migration (e.g. 048).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend-compliance/migration_runner.py

@@ -79,6 +79,7 @@ def run_migrations():
 
         logger.info("%d pending migrations (of %d total)", len(pending), len(migration_files))
 
+        failed = []
         for migration_file in pending:
             logger.info("Applying migration: %s", migration_file.name)
             try:
@@ -96,10 +97,13 @@ def run_migrations():
             except Exception as e:
                 raw_conn.rollback()
                 logger.error("  FAILED: %s — %s", migration_file.name, e)
-                raise RuntimeError(
-                    f"Migration {migration_file.name} failed: {e}"
-                ) from e
+                failed.append((migration_file.name, str(e)))
+                # Continue with remaining migrations instead of aborting
 
+        if failed:
+            names = ", ".join(f[0] for f in failed)
+            logger.error("Some migrations failed: %s", names)
+        else:
             logger.info("All migrations applied successfully")
     finally:
         raw_conn.close()