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/productivity/nextcloud/euro-office/Dockerfile

@@ -0,0 +1,4 @@
+FROM ghcr.io/euro-office/documentserver:latest
+
+# Internal-zone apps trust the fleet's own internal CA here (cert copied in,
+# then update-ca-certificates run) — the actual cert and paths are kept private.

stacks/productivity/nextcloud/nextcloud/Dockerfile

@@ -0,0 +1,10 @@
+FROM nextcloud:latest
+
+RUN apt-get update && \
+    apt-get install -y ca-certificates smbclient libsmbclient-dev && \
+    pecl install smbclient && \
+    docker-php-ext-enable smbclient && \
+    rm -rf /var/lib/apt/lists/*
+
+# Internal-zone apps trust the fleet's own internal CA here (cert copied in,
+# then update-ca-certificates run) — the actual cert and paths are kept private.