Regenerate Ai Analysis

Regenerate all AI analysis for a conversation (user clicks Re-analyze). Issue #640: runs summary + triage + reply synchronously (reads existing classification), stores results, and returns them. Opens its own DB session internally — the request-scoped ``db`` is not passed in. Usage event is recorded inside the orchestrator (single event).

curl -X POST "https://loading/api/v2/conversations/string/regenerate-ai-analysis"

{
  "copilot_context": {},
  "duration_ms": 0,
  "generated_at": "string",
  "suggested_reply": {}
}

{
  "detail": [
    {
      "loc": [
        "string"
      ],
      "msg": "string",
      "type": "string"
    }
  ]
}