feat(core,backends,frontends,storage): conversations, inject queue, session pool, gateway mcp tools, api frontend

src/beaver_gateway/storage/db.py

@@ -105,9 +105,29 @@ def _add_missing_columns(conn: Connection) -> None:
             if column.name in existing:
                 continue
             kind = column.type.compile(conn.dialect)
-            conn.execute(
-                text(f"ALTER TABLE {table.name} ADD COLUMN {column.name} {kind}")
-            )
+            ddl = f"ALTER TABLE {table.name} ADD COLUMN {column.name} {kind}"
+            default = _column_default(column)
+            if default is not None:
+                ddl += f" DEFAULT {default}"
+            conn.execute(text(ddl))
+
+
+def _column_default(column: Any) -> str | None:
+    """Literal for ``ADD COLUMN ... DEFAULT`` so old rows get the model default."""
+    server_default = getattr(column, "server_default", None)
+    if server_default is not None:
+        return str(server_default.arg.text)
+    default = getattr(column, "default", None)
+    if default is None or default.is_callable:
+        return None
+    value = default.arg
+    if isinstance(value, bool):
+        return "TRUE" if value else "FALSE"
+    if isinstance(value, int | float):
+        return repr(value)
+    if isinstance(value, str):
+        return "'" + value.replace("'", "''") + "'"
+    return None
 
 
 # ---- Token CRUD ---------------------------------------------------------