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/stores/executionStore.ts

@@ -5,6 +5,8 @@ import type ChatHistoryWidget from '@/components/graph/widgets/ChatHistoryWidget
 import { useNodeChatHistory } from '@/composables/node/useNodeChatHistory'
 import { useNodeProgressText } from '@/composables/node/useNodeProgressText'
 import type { LGraph, Subgraph } from '@/lib/litegraph/src/litegraph'
+import { isCloud } from '@/platform/distribution/types'
+import { useTelemetry } from '@/platform/telemetry'
 import type { ComfyWorkflow } from '@/platform/workflow/management/stores/workflowStore'
 import { useWorkflowStore } from '@/platform/workflow/management/stores/workflowStore'
 import type {
@@ -288,6 +290,11 @@ export const useExecutionStore = defineStore('execution', () => {
   }
 
   function handleExecutionSuccess() {
+    if (isCloud && activePromptId.value) {
+      useTelemetry()?.trackExecutionSuccess({
+        jobId: activePromptId.value
+      })
+    }
     resetExecutionState()
   }
 
@@ -352,6 +359,14 @@ export const useExecutionStore = defineStore('execution', () => {
 
   function handleExecutionError(e: CustomEvent<ExecutionErrorWsMessage>) {
     lastExecutionError.value = e.detail
+    if (isCloud) {
+      useTelemetry()?.trackExecutionError({
+        jobId: e.detail.prompt_id,
+        nodeId: String(e.detail.node_id),
+        nodeType: e.detail.node_type,
+        error: e.detail.exception_message
+      })
+    }
     resetExecutionState()
   }