fix(oauth): fix login failures and add provider icon_url config

- Fix FIND_OAUTH_LINKED_USER_SQL missing allowed_providers_mode columns
- Fix TOUCH_OAUTH_LINK_SQL json/jsonb type mismatch in COALESCE
- Add icon_url field to OAuth provider config (DB, API, frontend)
- Fix admin OAuth test: accept 404 as reachable, use system proxy

frontend/src/api/oauth.ts

@@ -3,6 +3,7 @@ import apiClient from './client'
 export interface OAuthProviderInfo {
   provider_type: string
   display_name: string
+  icon_url?: string | null
 }
 
 export interface OAuthProvidersResponse {
@@ -46,6 +47,7 @@ export interface OAuthProviderAdminConfig {
   frontend_callback_url: string
   attribute_mapping?: Record<string, unknown> | null
   extra_config?: Record<string, unknown> | null
+  icon_url?: string | null
   is_enabled: boolean
 }
 
@@ -61,6 +63,7 @@ export interface OAuthProviderUpsertRequest {
   frontend_callback_url: string
   attribute_mapping?: Record<string, unknown> | null
   extra_config?: Record<string, unknown> | null
+  icon_url?: string | null
   is_enabled: boolean
   force?: boolean
 }