docs: complete code-reality alignment for remaining docs + reconcile issue set

Remaining docs updated to match code (the docs that the first pass had not covered):
- Flows: Chat, Referral, Rating, Registration, Google OAuth, Negotiation, Payout,
  Trezor Safekeeping — corrected endpoints, socket events, status enums, auth gaps
- API Reference: User API, Trezor API — admin route prefix/verb/status corrections,
  added undocumented endpoints (ton-proof challenge, profile email verify,
  GET /trezor/account, POST /trezor/verify-operation)
- Data Models: Chat, Notification, Payment, PointTransaction, User — corrected
  enums (PaymentProvider, escrowState, PointTransaction.type, User.status),
  90-day notification TTL, soft-delete semantics, wallet fields

Trezor "zero frontend" finding (audit C31/C32) corrected as STALE:
- Verified current code HAS a full frontend Trezor implementation (admin/trezor
  page, TrezorSettingsView, trezorConnector via @trezor/connect-web,
  TrezorSignDialog, actions/trezor.ts building the {message,signature} object)
- Fixed Trezor Safekeeping Flow doc (removed false "no frontend" warnings)
- Reclassified ISSUE-012 as invalid/superseded with explanation

Issue set reconciled to a single canonical numbering (ISSUE-001..054):
- Adopted the comprehensive 51-issue set (long-slug, fully indexed)
- Removed 35 superseded short-slug duplicates from the first pass
- Removed a duplicate ISSUE-046 file
- Added 3 issues the 51-set lacked: ISSUE-052 (completed-not-counted-in-stats),
  ISSUE-053 (axios 401-only interceptor), ISSUE-054 (rate limiter counts all attempts)
- Regenerated Issues Index: 53 open (14 critical, 39 major) + 1 invalid

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

03 - API Reference/Payment API.md

@@ -500,6 +500,16 @@ Same result shape as above, but for a single destination.
 }
 ```
 
+## Frontend PaymentProvider type
+
+`src/types/payment.ts` defines `PaymentProvider` as:
+
+```ts
+type PaymentProvider = 'request.network' | 'test' | 'other';
+```
+
+> ⚠️ **Type gap (M37):** Despite both SHKeeper and the legacy wallet-direct (DePay/decentralized) flows being active in production, neither `'shkeeper'` nor `'decentralized'` appears in this union. Any frontend code that branches on `provider` will treat both as `'other'` or fall through a switch default. The backend stores the literal strings `"shkeeper"` and `"decentralized"` in the database; the mismatch exists only in the frontend type definition.
+
 ## Status model
 
 [[Payment]] uses the statuses below across all providers: