add session cookie auth on cloud dist (#6295)

## Summary

Implemented cookie-based session authentication for cloud distribution,
replacing service worker approach with extension-based lifecycle hooks.

## Changes

- **What**: Added session cookie management via [extension
hooks](https://docs.comfy.org/comfyui/extensions) for login, token
refresh, and logout events
- **Architecture**: DDD-compliant structure with platform layer
(`src/platform/auth/session/`) and cloud-gated extension
- **New Extension Hooks**: `onAuthTokenRefreshed()` and
`onAuthUserLogout()` in [ComfyExtension
interface](src/types/comfy.ts:220-232)

```mermaid
sequenceDiagram
    participant User
    participant Firebase
    participant Extension
    participant Backend

    User->>Firebase: Login
    Firebase->>Extension: onAuthUserResolved
    Extension->>Backend: POST /auth/session (with JWT)
    Backend-->>Extension: Set-Cookie

    Firebase->>Firebase: Token Refresh
    Firebase->>Extension: onAuthTokenRefreshed
    Extension->>Backend: POST /auth/session (with new JWT)
    Backend-->>Extension: Update Cookie

    User->>Firebase: Logout
    Firebase->>Extension: onAuthUserLogout (user null)
    Extension->>Backend: DELETE /auth/session
    Backend-->>Extension: Clear Cookie
```

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6295-add-session-cookie-auth-on-cloud-dist-2986d73d365081868c56e5be1ad0d0d4)
by [Unito](https://www.unito.io)

src/composables/auth/useCurrentUser.ts

@@ -1,5 +1,5 @@
 import { whenever } from '@vueuse/core'
-import { computed } from 'vue'
+import { computed, watch } from 'vue'
 
 import { useFirebaseAuthActions } from '@/composables/auth/useFirebaseAuthActions'
 import { t } from '@/i18n'
@@ -37,6 +37,15 @@ export const useCurrentUser = () => {
   const onUserResolved = (callback: (user: AuthUserInfo) => void) =>
     whenever(resolvedUserInfo, callback, { immediate: true })
 
+  const onTokenRefreshed = (callback: () => void) =>
+    whenever(() => authStore.tokenRefreshTrigger, callback)
+
+  const onUserLogout = (callback: () => void) => {
+    watch(resolvedUserInfo, (user) => {
+      if (!user) callback()
+    })
+  }
+
   const userDisplayName = computed(() => {
     if (isApiKeyLogin.value) {
       return apiKeyStore.currentUser?.name
@@ -133,6 +142,8 @@ export const useCurrentUser = () => {
     handleSignOut,
     handleSignIn,
     handleDeleteAccount,
-    onUserResolved
+    onUserResolved,
+    onTokenRefreshed,
+    onUserLogout
   }
 }