feat: add GET /api/v1/vouching/requests endpoint for incoming vouch requests

[daRk8238]

Summary

Mentors previously had no way to see who has requested a vouch from them. This PR adds GET /api/v1/vouching/requests so mentors can view all pending vouch requests for their wallet.

Changes

New endpoint

• GET /api/v1/vouching/requests — JWT-auth required (mentor wallet). Returns only pending requests where the authenticated user is the mentor, ordered newest-first.

Response shape (array of VouchRequestItemDto)

Field	Type	Source
learnerWallet	string	vouches.learner_wallet
reputationScore	number	reputation_cache.score (defaults to 0 on miss)
requestedLoanAmount	number | null	vouches.loan_amount
loanPurpose	string | null	vouches.message
requestedAt	string	vouches.created_at (ISO 8601)

Files touched

File	Change
src/modules/vouching/vouching.controller.ts	Added @Get('requests') handler with full Swagger decorators
src/modules/vouching/vouching.service.ts	Added getIncomingRequests() and getLearnerReputationScore()
src/modules/vouching/dto/vouch.dto.ts	Added VouchRequestItemDto with @ApiProperty annotations
supabase/migrations/20260619000001_add_vouch_request_fields.sql	Added loan_amount NUMERIC column to vouches table

Verification

• npm run build passes
• Full Swagger documentation on endpoint and response DTO
• Filters by authenticated wallet only (JWT currentUser.wallet)
• Includes learner reputation score from reputation_cache

Closes #21