fix(v2.2.0): migrate to new Miruro pipe protocol — restore streaming endpoints

The streaming endpoints (/episodes, /sources, /stream, /watch, /download)
returned 500 because the upstream Miruro pipe changed and www.miruro.tv is
now hard-blocked by Cloudflare.

Reverse-engineered the current Miruro frontend contract:
- Request is plain base64url of the JSON payload (no XOR).
- Response obfuscation is now signalled by the x-obfuscated header:
  absent = plain JSON, 1 = base64+gzip, 2 = base64+XOR(PIPE_OBF_KEY)+gzip.

pipe.js now:
- rotates across mirrors (miruro.ru > .to > .bz > .tv), one per retry;
- decodes based on the x-obfuscated header instead of always XOR+gunzip;
- sends full browser sec-fetch/sec-ch-ua headers to pass Cloudflare checks;
- raises maxRetries to 4 and rotates on 403/444.

proxy.js default referer/Origin -> https://www.miruro.to (miruro.tv is dead).

AniList-backed endpoints were already healthy and are unaffected.
Version bumped to 2.2.0 across package.json, server.js, /api/health,
/api/openapi, public/openapi.json. CHANGELOG updated.

public/openapi.json

@@ -3,7 +3,7 @@
   "info": {
     "title": "MiruroAPI",
     "description": "Free RESTful API for anime streaming data. Powered by AniList GraphQL and Miruro streaming providers.",
-    "version": "2.1.4",
+    "version": "2.2.0",
     "contact": {
       "name": "Shineii86",
       "url": "https://github.com/Shineii86/MiruroAPI"