fix(backend): standardize superset client init and auth

- Update plugins (debug, mapper, search) to explicitly map environment config to SupersetConfig
- Add authenticate method to SupersetClient for explicit session management
- Add get_environment method to ConfigManager
- Fix navbar dropdown hover stability in frontend with invisible bridge

backend/src/core/config_manager.py

@@ -186,6 +186,20 @@ class ConfigManager:
             return len(self.config.environments) > 0
     # [/DEF:has_environments:Function]
 
+    # [DEF:get_environment:Function]
+    # @PURPOSE: Returns a single environment by ID.
+    # @PRE: self.config is set and isinstance(env_id, str) and len(env_id) > 0.
+    # @POST: Returns Environment object if found, None otherwise.
+    # @PARAM: env_id (str) - The ID of the environment to retrieve.
+    # @RETURN: Optional[Environment] - The environment with the given ID, or None.
+    def get_environment(self, env_id: str) -> Optional[Environment]:
+        with belief_scope("get_environment"):
+            for env in self.config.environments:
+                if env.id == env_id:
+                    return env
+            return None
+    # [/DEF:get_environment:Function]
+
     # [DEF:add_environment:Function]
     # @PURPOSE: Adds a new environment to the configuration.
     # @PRE: isinstance(env, Environment)