Logic goes through the fallback vendors even when primary ones are returning results

[Aitous]

When configuring multiple primary vendors using comma-separated values (e.g., "news_data": "reddit,alpha_vantage"), the vendor routing logic in interface.py did not stop after attempting all primary vendors. Instead, it continued to attempt all fallback vendors, which is unintended behavior.

When multiple primary vendors are configured, the system should:

1. Attempt all specified primary vendors in order
2. Collect results from each successful primary vendor
3. Stop after all primary vendors have been attempted
4. Only use fallback vendors if a primary vendor fails

[kaushik-yadav]

I've submitted a PR with a fix for this issue:

PR: #292

The fix ensures the router stops after processing all primary vendors and only falls back when needed.