style: order environment variables by how much the service needs them

environment: blocks were in no particular order. They now run must-have ->
should-have -> optional, with related variables kept adjacent as a group that
takes the tier of its most important member: PUID/PGID, PASSWORD with
SUDO_PASSWORD, DOCKER_MODS ahead of the INSTALL_PACKAGES and
NODEJS_MOD_VERSION that configure it, the four GIT_* entries, the PASEO_*
daemon settings.

Each .env.example is reordered to match its compose file. The names do not map
one to one -- PASSWORD feeds both PASSWORD and SUDO_PASSWORD, SERVICE_HOSTNAME
feeds HOST -- so an entry sits where the first compose entry reading it sits.

The HOST comment in both compose files is dropped; the READMEs already carry
that explanation in full. CLAUDE.md records the ordering convention.

alloy and gitea-mirror-local are untouched: every variable there is required,
so the tiers collapse and the existing grouping is the better one.

code-server-base/compose.yml

@@ -4,11 +4,11 @@ services:
     environment:
       - PUID=1000
       - PGID=1000
+      - PASSWORD=${PASSWORD}
+      - SUDO_PASSWORD=${PASSWORD}
       - TZ=Asia/Ho_Chi_Minh
       - DEFAULT_WORKSPACE=/config/workspace
       - PWA_APPNAME=code-server
-      - PASSWORD=${PASSWORD}
-      - SUDO_PASSWORD=${PASSWORD}
     volumes:
       - 'code-server-config:/config'
 volumes: