v1.8.53: fix Redis and MariaDB GUI tabs — wrong client API calls

- redis_tab: fix RedisClient constructor (pass server dict, not alias+store)
- redis_tab: add connect() call, add disconnect on server switch
- redis_tab: remove non-existent db= parameter from execute(), use select_db()
- redis_client: add select_db() method for runtime DB switching
- query_tab: fix use_database() → switch_database(), close() → disconnect()
- query_tab: fix execute() → execute_query() with dict unpacking
- query_tab: add missing connect() call after SQLClient creation

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

core/redis_client.py

@@ -62,6 +62,13 @@ class RedisClient:
         except Exception:
             return False
 
+    def select_db(self, db: int):
+        """Switch to a different Redis database index."""
+        db = int(db)
+        if self._conn is not None and db != self._db:
+            self._conn.execute_command("SELECT", db)
+            self._db = db
+
     # -- commands ---------------------------------------------------------
 
     def execute(self, command: str) -> str: