Confidence/probability scores have no bounds validation

[jiya2401]

• TechSignal.confidence, ProductSignal.launch_probability, and ai_maturity_score are plain float fields with no range enforcement - the 0.0–1.0 (or 0–10) bounds only exist as a prompt instruction, not as code-level validation.
• If Gemini hallucinates an out-of-range value, Pydantic currently accepts it as-is and it flows straight into MongoDB and out to the frontend.
• Result: a broken/nonsensical UI with no validation layer catching it before storage.