fix(minimax): Bổ sung MiniMax-M3 + cập nhật Quota Tracker coding/CN

Squash-merge PR #1631 (decolua/9router) — chỉ lấy file code + test, bỏ docs.

- feat(minimax): add MiniMax-M3 to intl + cn provider models (targetFormat claude)
- feat(minimax): add MiniMax-M3 pricing entry
- fix(minimax): translate Claude body khi content=null (M3 thinking-only)
- fix(minimax): hiển thị quota M-series bucket "general"/"MiniMax-M*" + percent-only
- test: minimax usage / model registration / pricing

Co-Authored-By: Claude <noreply@anthropic.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

open-sse/config/providerModels.js

@@ -337,6 +337,7 @@ export const PROVIDER_MODELS = {
     { id: "kimi-latest", name: "Kimi Latest" },
   ],
   minimax: [
+    { id: "MiniMax-M3", name: "MiniMax M3", targetFormat: "claude" },
     { id: "MiniMax-M2.7", name: "MiniMax M2.7" },
     { id: "MiniMax-M2.5", name: "MiniMax M2.5" },
     { id: "MiniMax-M2.1", name: "MiniMax M2.1" },
@@ -363,6 +364,7 @@ export const PROVIDER_MODELS = {
     { id: "qwen3-vl-plus", name: "Qwen3 VL Plus" },
   ],
   "minimax-cn": [
+    { id: "MiniMax-M3", name: "MiniMax M3", targetFormat: "claude" },
     { id: "MiniMax-M2.7", name: "MiniMax M2.7" },
     { id: "MiniMax-M2.5", name: "MiniMax M2.5" },
     { id: "MiniMax-M2.1", name: "MiniMax M2.1" },