change cloud feature flags to be loaded dynamically at runtime rather than set in build (#6246)

## Summary

Implements server-side remote configuration to decouple runtime behavior
from build artifacts, enabling dynamic configuration updates without
redeployment.

## Technical Changes

- **Replaced** build-time constants (`__MIXPANEL_TOKEN__`,
`__BUILD_FLAGS__`) with runtime configuration loaded from
`/api/features`
- Configuration now sourced from `window.__CONFIG__` (hydrated from
`/api/features` endpoint)
- **Added** `src/platform/remoteConfig/` service that polls server
configuration every 30 seconds
- **Modified** application bootstrap sequence in `main.ts` to load
remote config before module initialization (required for cloud builds)
- **Removed** global constants: `__BUILD_FLAGS__`, `__MIXPANEL_TOKEN__`.
Runtime subscription enforcement toggle via `subscription_required` flag
- Server health alerts with variant-based severity rendering
(info/warning/error) via topbar badges

## Rationale

- **Build-once-deploy-anywhere**: Single immutable artifact promoted
through environments (staging → production)
- **Zero-downtime configuration**: Update behavior without rebuilding or
redeploying the application
- **Incident response**: Disable features or display alerts dynamically
in response to outages or degraded service
- **Instant rollback**: Revert configuration changes server-side without
artifact redeployment
- **Progressive delivery**: Enable A/B testing, canary releases, and
user/region-based configuration
- **Environment parity**: Eliminate configuration drift between staging
and production builds
- Decouples deployment cadence from configuration changes
- Enables GitOps workflows for configuration management separate from
code deployments
- Supports real-time operational control of client behavior
- Reduces build matrix complexity (no per-environment builds)

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6246-change-cloud-feature-flags-to-be-loaded-dynamically-at-runtime-rather-than-set-in-build-2966d73d3650811cbb41c9093961037a)
by [Unito](https://www.unito.io)

src/extensions/core/cloudBadge.ts

@@ -1,12 +0,0 @@
-import { t } from '@/i18n'
-import { useExtensionService } from '@/services/extensionService'
-
-useExtensionService().registerExtension({
-  name: 'Comfy.CloudBadge',
-  topbarBadges: [
-    {
-      label: t('g.beta'),
-      text: 'Comfy Cloud'
-    }
-  ]
-})

src/extensions/core/cloudBadges.ts

@@ -0,0 +1,36 @@
+import { computed } from 'vue'
+
+import { remoteConfig } from '@/platform/remoteConfig/remoteConfig'
+import { t } from '@/i18n'
+import { useExtensionService } from '@/services/extensionService'
+import type { TopbarBadge } from '@/types/comfy'
+
+const badges = computed<TopbarBadge[]>(() => {
+  const result: TopbarBadge[] = []
+
+  // Add server health alert first (if present)
+  const alert = remoteConfig.value.server_health_alert
+  if (alert) {
+    result.push({
+      text: alert.message,
+      label: alert.badge,
+      variant: alert.severity ?? 'error',
+      tooltip: alert.tooltip
+    })
+  }
+
+  // Always add cloud badge last (furthest right)
+  result.push({
+    label: t('g.beta'),
+    text: 'Comfy Cloud'
+  })
+
+  return result
+})
+
+useExtensionService().registerExtension({
+  name: 'Comfy.Cloud.Badges',
+  get topbarBadges() {
+    return badges.value
+  }
+})

src/extensions/core/cloudRemoteConfig.ts

@@ -0,0 +1,15 @@
+import { loadRemoteConfig } from '@/platform/remoteConfig/remoteConfig'
+import { useExtensionService } from '@/services/extensionService'
+
+/**
+ * Cloud-only extension that polls for remote config updates
+ * Initial config load happens in main.ts before any other imports
+ */
+useExtensionService().registerExtension({
+  name: 'Comfy.Cloud.RemoteConfig',
+
+  setup: async () => {
+    // Poll for config updates every 30 seconds
+    setInterval(() => void loadRemoteConfig(), 30000)
+  }
+})

src/extensions/core/cloudSubscription.ts

@@ -4,8 +4,11 @@ import { useCurrentUser } from '@/composables/auth/useCurrentUser'
 import { useSubscription } from '@/platform/cloud/subscription/composables/useSubscription'
 import { useExtensionService } from '@/services/extensionService'
 
+/**
+ * Cloud-only extension that enforces active subscription requirement
+ */
 useExtensionService().registerExtension({
-  name: 'Comfy.CloudSubscription',
+  name: 'Comfy.Cloud.Subscription',
 
   setup: async () => {
     const { isLoggedIn } = useCurrentUser()
@@ -13,7 +16,6 @@ useExtensionService().registerExtension({
 
     const checkSubscriptionStatus = () => {
       if (!isLoggedIn.value) return
-
       void requireActiveSubscription()
     }
 

src/extensions/core/index.ts

@@ -24,10 +24,12 @@ import './uploadImage'
 import './webcamCapture'
 import './widgetInputs'
 
+// Cloud-only extensions - tree-shaken in OSS builds
 if (isCloud) {
-  import('./cloudBadge')
+  await import('./cloudRemoteConfig')
+  await import('./cloudBadges')
 
-  if (__BUILD_FLAGS__.REQUIRE_SUBSCRIPTION) {
-    import('./cloudSubscription')
+  if (window.__CONFIG__?.subscription_required) {
+    await import('./cloudSubscription')
   }
 }