refactor: saasMode 분기 제거 — 항상 SaaS(OAuth only)로 동작

Mac/Windows 환경 불일치 해소. BUILD_TIME 상수, CONFIGURE 채널,
개발자 모드 UI 전부 제거. Supabase 설정은 supabase-config.ts SSOT.

apps/desktop/src/main/ipc/cloud-sync-handlers.ts

@@ -6,7 +6,6 @@ import { IPC_CHANNELS } from '@d3ro/core/ipc-channels'
 import { D3ROError, ErrorCode } from '@d3ro/core/errors'
 import type { IPCResult } from '@d3ro/core/errors'
 import { getCloudSyncService } from '../services/CloudSyncService'
-import { configSet } from '../services/ConfigService'
 import { getLogger } from '../services/LoggerService'
 
 const logger = getLogger('cloud-sync-handlers')
@@ -15,11 +14,6 @@ interface SignInParams {
   provider: 'google' | 'github'
 }
 
-interface ConfigureParams {
-  url: string
-  anonKey: string
-}
-
 function ok<T>(data: T): IPCResult<T> {
   return { success: true, data }
 }
@@ -46,18 +40,6 @@ export function registerCloudSyncHandlers(): void {
     }
   })
 
-  ipcMain.handle(IPC_CHANNELS.CLOUD_SYNC.CONFIGURE, async (_e, params: ConfigureParams) => {
-    try {
-      configSet('supabaseUrl' as never, params.url as never)
-      configSet('supabaseAnonKey' as never, params.anonKey as never)
-      // CloudSyncService 재초기화
-      await sync.init()
-      return ok(sync.getState())
-    } catch (e) {
-      return fail(e)
-    }
-  })
-
   ipcMain.handle(IPC_CHANNELS.CLOUD_SYNC.SIGN_IN, async (_e, params: SignInParams) => {
     try {
       await sync.startSignIn(params.provider)