Add analytics for workflow loading (#4966)

Needs to land after https://github.com/Comfy-Org/cloud/pull/398

## Description

- Adds a postCloudAnalytics method in `api.ts`
- Adds a workflow_loaded event
- The event contains 
  - the source (not file type, more like workflow format) one of: 
    - apiJson (I think this is the "prompt" format?)
    - graph (the richest type)
    - template: don't fully understand this but it works
- The actual data for the workflow, depends on the source type
- If available, missingModels and missingNodeTypes, so we can easily
query those

This talks to a new endpoint on the ingest server that is being added.  

## Tests
Tested manually with:
- loading an image from civitAI with missing models
- loading an image from comfy examples with no missing models
- opening a json file in the prompt format (I asked claude to generate
one - this is the format handled by the loadApiJson function)
- opening a template file (claude generated one - this is the format
handled by loadTemplateJson function)
- Testing these for both dragAndDrop and (menu --> open --> open
workflow)

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-4966-Add-analytics-for-workflow-loading-24e6d73d36508170acacefb3125b7017)
by [Unito](https://www.unito.io)

src/scripts/api.ts

@@ -1275,6 +1275,28 @@ export class ComfyApi extends EventTarget {
   getServerFeatures(): Record<string, unknown> {
     return { ...this.serverFeatureFlags }
   }
+
+  /**
+   * Posts analytics event to cloud analytics service
+   * @param eventName The name of the analytics event
+   * @param eventData The event data (any JSON-serializable object)
+   * @returns Promise resolving to the response
+   */
+  async postCloudAnalytics(
+    eventName: string,
+    eventData: any
+  ): Promise<Response> {
+    return this.fetchApi(this.internalURL('/cloud_analytics'), {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json'
+      },
+      body: JSON.stringify({
+        event_name: eventName,
+        event_data: eventData
+      })
+    })
+  }
 }
 
 export const api = new ComfyApi()