Add config updates via SSE (behind FF)

[timokoessler]

Feature Flag env: AIKIDO_FEATURE_SSE

Summary by Aikido

Security Issues: 0	🔍 Quality Issues: 1	Resolved Issues: 0

🚀 New Features

• Added SSE client, parser and listener for config updates.

⚡ Enhancements

• Switched realtime URL and config fetch to use get_api_url.

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