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.

package.json

@@ -1,7 +1,7 @@
 {
   "name": "miruro-api",
-  "version": "2.1.4",
-  "description": "RESTful API for miruro.tv - Anime streaming data powered by AniList GraphQL and Miruro streaming providers",
+  "version": "2.2.0",
+  "description": "RESTful API for Miruro - Anime streaming data powered by AniList GraphQL and Miruro streaming providers",
   "main": "server.js",
   "scripts": {
     "start": "node server.js",