FAISS Similarity Matching & Score Fusion (US-4.3) - 3 SP

[sainijit]

User story
As a developer, I want to search embeddings against FAISS and apply a weighted scoring fusion formula, so that users can be authenticated.

Affected Components / Files

• identity-service/

Key Technical Tasks

• Implement FAISS similarity lookups.
• Implement fusion formula: Score = 0.6 * Sim_face + 0.4 * Sim_voice.
• Handle fallback thresholds for single indicators.

Acceptance Criteria

• Search retrieves correct loyalty offsets. Validates and logs in matching users; rejects unauthorized inputs.

Estimate: 3 SP