Refactor proxy-core surfaces and transformer boundaries (#163)

* refactor: add canonical request contracts

* test: harden transformer boundary contracts

* refactor: adapt protocol transformers to canonical contract

* refactor: add cli profile registry

* refactor: extract provider profiles

* refactor: add conductor and provider executors

* refactor: add models surface

* refactor: migrate responses surface

* refactor: migrate chat surface

* refactor: migrate gemini surface

* refactor: migrate file surfaces

* test: align runtime executor undici mock

* fix: preserve compact SSE closeout payloads

* feat: support all-api-hub v2 backup imports

* fix: aggregate codex oauth SSE final payloads

* fix: harden responses SSE failure handling

src/server/routes/api/stats.ts

@@ -25,6 +25,7 @@ import {
   getLocalDayRangeUtc,
   getLocalRangeStartUtc,
   parseStoredUtcDateTime,
+  type StoredUtcDateTimeInput,
   toLocalDayKeyFromStoredUtc,
 } from '../../services/localTimeService.js';
 import { createRateLimitGuard } from '../../middleware/requestRateLimit.js';
@@ -202,7 +203,7 @@ type SiteAvailabilitySiteRow = {
 
 type SiteAvailabilityLogRow = {
   siteId: number | null;
-  createdAt: string | null;
+  createdAt: StoredUtcDateTimeInput;
   status: string | null;
   latencyMs: number | null;
 };