Add support for image attachments in chat messages and update model capabilities endpoint

backend/database.py

@@ -4,16 +4,15 @@ from sqlalchemy.orm import sessionmaker, DeclarativeBase
 from sqlalchemy import text
 
 """
-Database utilities and configuration.  This module defines the SQLAlchemy
-engine, session factory and base class for models.  It also contains a
-lightweight migration helper used to evolve the schema over time.  The
-`ensure_sources_column` helper adds a new `sources_json` column to the
-`chat_messages` table if it does not already exist.  This is required
-for persisting citation sources alongside assistant messages.
+Database utilities and configuration. This module defines the SQLAlchemy
+engine, session factory and base class for models. It also contains a
+lightweight migration helper used to evolve the schema over time. The
+`ensure_sources_column` helper adds the JSON-backed columns used by chat
+messages when they do not already exist.
 
 The migration uses SQLite's `ALTER TABLE` syntax and therefore should
-only run once on startup.  It is safe to call repeatedly: when the
-column already exists, the function will simply no‑op.
+only run once on startup. It is safe to call repeatedly: when a column
+already exists, the function will simply no-op.
 """
 
 DATABASE_URL = "sqlite:///./backend/app.db"
@@ -34,5 +33,7 @@ def ensure_sources_column(engine):
             cols = [row[1] for row in conn.execute(text("PRAGMA table_info(chat_messages)"))]
             if "sources_json" not in cols:
                 conn.execute(text("ALTER TABLE chat_messages ADD COLUMN sources_json TEXT DEFAULT '[]'"))
+            if "attachments_json" not in cols:
+                conn.execute(text("ALTER TABLE chat_messages ADD COLUMN attachments_json TEXT DEFAULT '[]'"))
     except Exception as e:
         print("[db] ensure_sources_column error:", e)