serve assets and the store archive from gitea-watch (the GitHub repo is gone)

github.com/Worph/MetaAppStore answers 404, and with it every jsDelivr
cdn.jsdelivr.net/gh/Worph/MetaAppStore@main/ URL: the icons, thumbnails and
screenshots of all 44 apps were missing from the store listing, and the store
source in the README no longer downloaded.

- Asset URLs in every Apps/*/docker-compose.yml now point at
  https://gitea-watch.nsl.sh/metastar/MetaAppStore/raw/branch/main/Apps/{AppName}/
  (103 of the 109 distinct URLs checked: 200 image/png). The other 6, MetaGateway
  and MetaWatch screenshot-1..3, name files that have never been in this repo.
- README: the store source is https://gitea-watch.nsl.sh/metastar/MetaAppStore/archive/main.zip
  (public, checked to download anonymously).
- CLAUDE.md and CONTRIBUTING.md: the asset rule and its grep guard follow, so an
  import cannot bring back a jsDelivr URL unnoticed.

README.md

@@ -11,7 +11,7 @@ collection.
 In Yundera / CasaOS → App Store → *Add source*:
 
 ```
-https://github.com/Worph/MetaAppStore/archive/refs/heads/main.zip
+https://gitea-watch.nsl.sh/metastar/MetaAppStore/archive/main.zip
 ```
 
 ## What's in here
@@ -40,10 +40,11 @@ tier `MetaFeederSuwayomi` reads) and **SegmentPlayer**.
 
 ## Assets
 
-Icons and screenshots are served from jsDelivr:
+Icons and screenshots are served by Gitea, as raw files of this repo (the GitHub
+repo, and with it the jsDelivr `gh/Worph/...` URLs, is gone):
 
 ```
-https://cdn.jsdelivr.net/gh/Worph/MetaAppStore@main/Apps/{AppName}/
+https://gitea-watch.nsl.sh/metastar/MetaAppStore/raw/branch/main/Apps/{AppName}/
 ```
 
 `psd-source/meta-icons-v2/` holds the procedural icon generator for the family —