feat: add DELETE /repos/{repo_id} endpoint

Bug fix: Settings page 'Delete All' was calling non-existent endpoint

Backend:
- Add DELETE /repos/{repo_id} route with ownership verification
- Add repo_manager.delete_repo() method that:
  - Deletes from Supabase (cascades to embeddings, dependencies)
  - Cleans up local clone directory
  - Removes from in-memory cache

This completes the Settings page danger zone functionality.

Author: DevanshuNEU

backend/routes/repos.py

@@ -146,6 +146,35 @@ async def add_repository(
         raise HTTPException(status_code=400, detail=str(e))
 
 
+@router.delete("/{repo_id}")
+async def delete_repository(
+    repo_id: str,
+    auth: AuthContext = Depends(require_auth)
+):
+    """Delete a repository and all its indexed data."""
+    user_id = auth.user_id
+    
+    if not user_id:
+        raise HTTPException(status_code=401, detail="User ID required")
+    
+    # Verify ownership
+    repo = get_repo_or_404(repo_id, user_id)
+    
+    try:
+        success = repo_manager.delete_repo(repo_id)
+        if not success:
+            raise HTTPException(status_code=500, detail="Failed to delete repository")
+        
+        logger.info("Repository deleted", repo_id=repo_id, user_id=user_id)
+        return {"message": "Repository deleted successfully"}
+    except HTTPException:
+        raise
+    except Exception as e:
+        logger.error("Failed to delete repository", repo_id=repo_id, error=str(e))
+        capture_exception(e)
+        raise HTTPException(status_code=500, detail=str(e))
+
+
 @router.post("/{repo_id}/index")
 async def index_repository(
     repo_id: str,

backend/services/repo_manager.py

@@ -156,3 +156,30 @@ def get_last_indexed_commit(self, repo_id: str) -> str:
     def update_last_commit(self, repo_id: str, commit_sha: str, function_count: int = 0):
         """Update last indexed commit"""
         self.db.update_last_indexed(repo_id, commit_sha, function_count)
+    
+    def delete_repo(self, repo_id: str) -> bool:
+        """Delete repository and clean up local files"""
+        import shutil
+        
+        repo = self.get_repo(repo_id)
+        if not repo:
+            return False
+        
+        # Delete from database (cascades to embeddings, dependencies, etc.)
+        self.db.delete_repository(repo_id)
+        
+        # Clean up local clone if it exists
+        local_path = repo.get("local_path")
+        if local_path and Path(local_path).exists():
+            try:
+                shutil.rmtree(local_path)
+                logger.info("Deleted local repo files", repo_id=repo_id, path=local_path)
+            except Exception as e:
+                logger.warning("Failed to delete local files", repo_id=repo_id, error=str(e))
+        
+        # Remove from in-memory cache
+        if repo_id in self.repos:
+            del self.repos[repo_id]
+        
+        logger.info("Deleted repository", repo_id=repo_id)
+        return True