chore(oss): audit the server package and resync the SDK mirrors

Split the 657-line operation service into eor, submit, and verify
modules, add the AGENT_REVOKED and KEY_RETIRED codes the Backend already
emits, and condense every multi-line comment. Mirror Node, Python, and
Go at 2.1.0 with the deep-health 503, non-idempotent retry, rotation
grace, and path-encoding fixes. Document which routes and response
fields the self-hosted server does not provide.

Claude-Session: https://claude.ai/code/session_01Agoc9bRVE9KL7mmWtey9Vq

packages/server/src/middleware/i18n.ts

@@ -1,11 +1,4 @@
-/**
- * i18n middleware — language detection from Accept-Language header.
- *
- * Reads the Accept-Language request header, detects the preferred
- * language (English or Chinese), and stores it in the Hono context
- * so that all downstream handlers and services can access it via
- * `c.get('lang')`.
- */
+/** i18n middleware: language detection from Accept-Language header. */
 
 import type { MiddlewareHandler } from 'hono';
 import type { Env, AppVariables } from '../types.js';