Fix tool refresh for OAuth

[madhav165]

🐛 Bug-fix PR

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📌 Summary

• Fixes issue of tool refresh for OAuth when tools already exist in database
• Creates helper functions to create list of truly new tools, prompts, resources to create after gateway refresh
• Uses them in update_gateway, toggle_gateway_status (during activation) and fetch_tools_after_oauth
• Updates the above functions to remove tools, prompts, resources not sent in latest call to gateway
• Creates new test cases for addition and deletion

🐞 Root Cause

• For OAuth, the update mechanism did not check if tool update is needed in db
• For other gateways, the update mechanism was not consistent between update_gateway and toggle_gateway_status
• The logic was not consistent between tools, prompts and resources

🧪 Verification

Check	Command	Status
Lint suite	make lint	pass
Unit tests	make test	pass
Manual regression no longer fails	steps / screenshots	Tested with OAuth GitHub server and an SSE server without auth

📐 MCP Compliance (if relevant)

• No breaking change to MCP clients

✅ Checklist

• Code formatted (make black isort pre-commit)
• No secrets/credentials committed

[crivetimihai]

Rebased & tested