Move price badges to python nodes (#7816)

## Summary

Backend part: https://github.com/Comfy-Org/ComfyUI/pull/11582

- Move API node pricing definitions from hardcoded frontend functions to
backend-defined JSONata expressions
- Add `price_badge` field to node definition schema containing JSONata
expression and dependency declarations
- Implement async JSONata evaluation with signature-based caching for
efficient reactive updates
- Show one decimal in credit badges when meaningful (e.g., 1.5 credits
instead of 2 credits)

## Screenshots (if applicable)

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┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7816-Move-price-badges-to-python-nodes-2da6d73d365081ec815ef61f7e3c65f7)
by [Unito](https://www.unito.io)

src/stores/nodeDefStore.ts

@@ -14,7 +14,8 @@ import type {
 import type {
   ComfyInputsSpec as ComfyInputSpecV1,
   ComfyNodeDef as ComfyNodeDefV1,
-  ComfyOutputTypesSpec as ComfyOutputSpecV1
+  ComfyOutputTypesSpec as ComfyOutputSpecV1,
+  PriceBadge
 } from '@/schemas/nodeDefSchema'
 import { NodeSearchService } from '@/services/nodeSearchService'
 import { useSubgraphStore } from '@/stores/subgraphStore'
@@ -66,6 +67,12 @@ export class ComfyNodeDefImpl
    * Order of inputs for each category (required, optional, hidden)
    */
   readonly input_order?: Record<string, string[]>
+  /**
+   * Price badge definition for API nodes.
+   * Contains a JSONata expression to calculate pricing based on widget values
+   * and input connectivity.
+   */
+  readonly price_badge?: PriceBadge
 
   // V2 fields
   readonly inputs: Record<string, InputSpecV2>
@@ -134,6 +141,7 @@ export class ComfyNodeDefImpl
     this.output_name = obj.output_name
     this.output_tooltips = obj.output_tooltips
     this.input_order = obj.input_order
+    this.price_badge = obj.price_badge
 
     // Initialize V2 fields
     const defV2 = transformNodeDefV1ToV2(obj)