fix(firestore): prevent double database write on file rename upload

[vibhutomer]

Fix: Prevent Double-Write Quota Drain in Cloud Uploads

Related Issue

• Closes Double Database Write on Duplicate File Upload #71

Description of Changes

• Fixed a control-flow bug in the uploadFileToCloud function (firestore.ts).
• When resolving a duplicate filename, the code previously saved the new file but fell through to execute a second setDoc operation.
• Added if (onSuccess) onSuccess(); and a return; statement immediately after the conflict-resolution upload.

Impact

• Cost Optimization: Cuts Firebase database writes in half when users resolve naming conflicts.
• Network Stability: Prevents concurrent duplicate POST requests to the backend.
• Bug Prevention: Stops the onSuccess callback from firing twice, which could cause erratic UI behavior.