feat(migration): implement interactive mapping resolution workflow

- Add SQLite database integration for environments and mappings
- Update TaskManager to support pausing tasks (AWAITING_MAPPING)
- Modify MigrationPlugin to detect missing mappings and wait for resolution
- Add frontend UI for handling missing mappings interactively
- Create dedicated migration routes and API endpoints
- Update .gitignore and project documentation

backend/src/api/routes/environments.py

@@ -0,0 +1,75 @@
+# [DEF:backend.src.api.routes.environments:Module]
+#
+# @SEMANTICS: api, environments, superset, databases
+# @PURPOSE:   API endpoints for listing environments and their databases.
+# @LAYER:     API
+# @RELATION:  DEPENDS_ON -> backend.src.dependencies
+# @RELATION:  DEPENDS_ON -> backend.src.core.superset_client
+#
+# @INVARIANT: Environment IDs must exist in the configuration.
+
+# [SECTION: IMPORTS]
+from fastapi import APIRouter, Depends, HTTPException
+from typing import List, Dict, Optional
+from backend.src.dependencies import get_config_manager
+from backend.src.core.superset_client import SupersetClient
+from superset_tool.models import SupersetConfig
+from pydantic import BaseModel
+# [/SECTION]
+
+router = APIRouter(prefix="/api/environments", tags=["environments"])
+
+# [DEF:EnvironmentResponse:DataClass]
+class EnvironmentResponse(BaseModel):
+    id: str
+    name: str
+    url: str
+# [/DEF:EnvironmentResponse]
+
+# [DEF:DatabaseResponse:DataClass]
+class DatabaseResponse(BaseModel):
+    uuid: str
+    database_name: str
+    engine: Optional[str]
+# [/DEF:DatabaseResponse]
+
+# [DEF:get_environments:Function]
+# @PURPOSE: List all configured environments.
+# @RETURN:  List[EnvironmentResponse]
+@router.get("", response_model=List[EnvironmentResponse])
+async def get_environments(config_manager=Depends(get_config_manager)):
+    envs = config_manager.get_environments()
+    return [EnvironmentResponse(id=e.id, name=e.name, url=e.url) for e in envs]
+# [/DEF:get_environments]
+
+# [DEF:get_environment_databases:Function]
+# @PURPOSE: Fetch the list of databases from a specific environment.
+# @PARAM:   id (str) - The environment ID.
+# @RETURN:  List[Dict] - List of databases.
+@router.get("/{id}/databases")
+async def get_environment_databases(id: str, config_manager=Depends(get_config_manager)):
+    envs = config_manager.get_environments()
+    env = next((e for e in envs if e.id == id), None)
+    if not env:
+        raise HTTPException(status_code=404, detail="Environment not found")
+    
+    try:
+        # Initialize SupersetClient from environment config
+        # Note: We need to map Environment model to SupersetConfig
+        superset_config = SupersetConfig(
+            env=env.name,
+            base_url=env.url,
+            auth={
+                "provider": "db", # Defaulting to db provider
+                "username": env.username,
+                "password": env.password,
+                "refresh": "false"
+            }
+        )
+        client = SupersetClient(superset_config)
+        return client.get_databases_summary()
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=f"Failed to fetch databases: {str(e)}")
+# [/DEF:get_environment_databases]
+
+# [/DEF:backend.src.api.routes.environments]