- config: add optional configPaths parameter to load() for test isolation
(tests now use t.TempDir() to avoid interference from D:\app\data)
- handler: fix stubAccountRepoForHandler.ListByPlatform to return accounts
(was returning nil, nil causing "no available accounts" errors)
- logger: fix Sync() blocking on Windows pipes by closing write end first
(also add Reset() function to close lumberjack file handles for cleanup)
P0 fixes:
- ModelError.Is(): use exact matching instead of substring contains()
- shouldClearStickySession: add context param for cancellation/tracing
P1 fixes:
- TODO stubs: return 501 Not Implemented errors
- validateInstanceSignature: deduplicate to shared validateCodeSignature()
- Error messages: standardize to English only
- http.go: remove pseudo if-else with duplicate branches
