Add animekai source with 1anime direct-MP4 backend (independent CDN)

animekai.be fronted two server backends per episode: megaplay.buzz
(same player/CDN family as hianime — 403s our egress IP) and
my.1anime.site (direct progressive MP4, independent CDN — verified
serving our IP at ~2.4MB/s). This is the rescue path around the
MegaPlay Cloudflare block, per the ani-cli #1945/#1918 work.

- providers/animekai.py: standard interface, per-episode backend
  dispatch (1anime first, then megaplay), same listed-but-dead ->
  raise semantics as hianime. All endpoints ride the shared TTL cache
  (no re-fetching on repeat UI hits).
- upstream.py: megaplay_master() moved out of hianime — the MegaPlay
  chain (embed -> data-id -> getSourcesNew -> enc decrypt -> CDN proof)
  is now shared by every provider fronting that player.
- app.py: /stream forwards Range for progressive files (206 +
  Content-Range passthrough, partial bodies never LRU-cached, 8MB cap
  on the parallel path so a 250MB MP4 can't pin RAM). api_stream
  reports hls=true/false from the URL — the player kind is a property
  of the URL, so future stream types slot in without app changes.
- app.js: hls===false -> native <video> (existing Range-seeking),
  hls.js path untouched.
- run.sh: ANI_SOURCE=animekai,hianime,anidb,anikoto (revert to the old
  chain when the MegaPlay block lifts).
- tests: test_animekai.py (offline: interface, enc decrypt, /stream
  Range via monkeypatched network) + test_animekai_live.py (opt-in
  ANI_LIVE=1 end-to-end, skipped by default so the suite never touches
  animekai.be).

server/providers/hianime.py

@@ -13,7 +13,7 @@ import json
 import re
 from urllib.parse import urljoin, urlparse
 
-from ..upstream import _cached, _get, megaplay_sources
+from ..upstream import _cached, _get, megaplay_master
 
 BASE = "https://hianime.at"
 KEY = b"otaku-embed-v1"
@@ -88,9 +88,8 @@ def _embed_payload(embed):
     """embed url -> (master_m3u8, [{label, src} subs], referer_or_None).
 
     Two player chains have appeared: zokoanime (window.__P blob,
-    base64+XOR) and megaplay (page needs the hianime referer; data-id ->
-    getSourcesNew; CDN domains rotate and most 403 us, so re-roll until
-    one serves)."""
+    base64+XOR — hianime-specific) and megaplay (shared: upstream.
+    megaplay_master, used by animekai too)."""
     page = _get(embed, timeout=15).text
     blob = re.search(r'window\.__P="([^"]+)"', page)
     if blob:
@@ -98,30 +97,7 @@ def _embed_payload(embed):
         subs = [{"label": (x or {}).get("label", ""), "src": (x or {}).get("src")}
                 for x in j.get("subtitles") or []]
         return j.get("src"), subs, re.match(r'https?://[^/]+', embed).group(0) + "/"
-    # megaplay: without the hianime referer the page is an error stub with no data-id
-    if not re.search(r'data-id="\d+"', page):
-        page = _get(embed, headers={"Referer": BASE + "/"}, timeout=15).text
-    mid = re.search(r'data-id="(\d+)"', page)
-    if not mid:
-        return None, [], None
-    host = re.match(r'https?://([^/]+)', embed).group(1)
-    # ponytail: one attempt — the enc payload is deterministic per data-id,
-    # so re-rolling getSourcesNew would just spam the provider
-    d = megaplay_sources(_get(f"https://{host}/stream/getSourcesNew?id={mid.group(1)}",
-             headers={"Referer": embed, "X-Requested-With": "XMLHttpRequest"},
-             timeout=15).json())
-    src = (d.get("sources") or {}).get("file")
-    if not src:
-        return None, [], None
-    subs = [{"label": (x or {}).get("label", ""), "src": (x or {}).get("file")}
-            for x in d.get("tracks") or []]
-    for cand, refr in (({"Referer": embed}, embed), ({}, None)):
-        try:
-            _get(src, headers=cand, timeout=10)
-            return src, subs, refr
-        except Exception:
-            continue
-    return None, [], None
+    return megaplay_master(embed, BASE + "/")
 
 
 def _master_m3u8(ep_id, lang="eng"):