feat(models): add paid tencent/hy3-preview route on OpenRouter (#21077)

Add tencent/hy3-preview (without :free suffix) as a paid model route
alongside the existing free variant. This allows seamless transition
when the model moves from free to paid on OpenRouter — both routes
coexist so neither side's timing causes breakage.

Changes:
- models.py: add ("tencent/hy3-preview", "") to OPENROUTER_MODELS
- model-catalog.json: add paid variant entry
- tests: add assertions for paid route presence

The :free entry can be removed in a follow-up PR once OpenRouter
confirms the free route is deprecated.

Co-authored-by: simonweng <simonweng@tencent.com>

website/static/api/model-catalog.json

@@ -68,6 +68,10 @@
           "id": "tencent/hy3-preview:free",
           "description": "free"
         },
+        {
+          "id": "tencent/hy3-preview",
+          "description": ""
+        },
         {
           "id": "openai/gpt-5.3-codex",
           "description": ""