stacks: add nextcloud Dockerfiles, fix a broken kodi compose edit

Adds the two Dockerfiles nextcloud's compose build: contexts were
already referencing but never had (custom smbclient support for the
main container, a documentserver base for euro-office) - both had
their real internal-CA-trust mechanism replaced with a comment
explaining what's there and why, per the standing rule against
publishing that detail.

Also fixes a compose bug: kodi-ma-bridge's `environment:` key had
been dropped, leaving KEY=value pairs nested under `env_file:` (which
expects file paths, not inline vars) - would have made docker-compose
try to open a file literally named `TZ=${TZ}`.

Rest of this commit is manual cleanup (comment tidying, dropped
personal media-library volume mounts, a couple of .env comment
trims).

stacks/media/tinymediamanager/docker-compose.yaml

@@ -12,10 +12,7 @@ services:
       - /path/to/tinymediamanager/data:/data
       - /path/to/tinymediamanager/config/launcher-extra.yml:/app/launcher-extra.yml
       - /path/to/media/movies:/media/movies
-      - /path/to/media/moviesetsartwork:/media/moviesetsartwork
       - /path/to/media/tv:/media/tv shows
-      - /path/to/media/documentaries:/media/documentaries
-      - /path/to/media/stand-up comedy:/media/stand-up comedy
     restart: unless-stopped
     networks:
       - media-net