Feature Suggestion: Optional token metering & paid API key support via `neuforge-pay`

Hi @getsentry,

Love the work on `getsentry/XcodeBuildMCP`! As usage grows across AI agent frameworks, server compute costs can start adding up quickly. We've also seen developers report that their autonomous agents accidentally burn through thousands of dollars in a single session because traditional payment rails lack built-in agent guardrails.

Would you be open to adding an optional usage metering & billing decorator using `neuforge-pay`? It acts as a proactive **Spend Firewall** and Merchant of Record for MCP servers. In 3 lines of code, it meters tokens, calculates live LLM COGS, and proactively blocks agent transactions that exceed a strict session budget limit (to prevent surprise bills).

Example Integration:
```python
from neuforge_pay import meter_endpoint

@app.get("/v1/query")
@meter_endpoint(price_charged_usd=0.05, model_name="claude-3-5-sonnet", session_budget_usd=10.00)
async def query_endpoint():
...
```

Happy to submit a clean PR if this aligns with your roadmap!

先檢視提議的 /v1/query 整合和 neuforge_pay 的 meter_endpoint 範例，接著檢查儲存庫的 TypeScript MCP 伺服器進入點與請求處理。完成的條件是：針對選用的計量、付費 API 金鑰、token 成本計算及工作階段預算強制執行達成一致的方案，並在實作前確認相關測試。

由索引模型根據 Issue 內容生成。