Phase 3.4 -- Approval & Meeting Response Extensions

Parent: #762

Context

Minor extensions to existing endpoints to support richer dashboard displays.

Scope

Extend approval responses

• Add seconds_remaining (computed from expires_at - now)
• Add urgency_level enum: critical (< 1hr), high (< 4hrs), normal (>= 4hrs), no_expiry
• Apply to both list and detail endpoints

Extend meeting responses

• Add token_usage_by_participant: {agent_name: token_count}
• Add contribution_rank: sorted list of agents by contribution
• Add meeting_duration_seconds (if completed)

Extend budget records response

• Add daily_summary aggregation of returned records
• Add period_summary stats (avg cost per record, total tokens)

Deliverables

• Approval responses include urgency data
• Meeting responses include per-participant token usage
• Budget records include summary aggregations
• Unit tests for computed fields
• OpenAPI schema updated