Nextcloud: refactor Talk → HPB, switch to bridge mode, and template cleanups

- Change Talk (HPB) network_mode from host → bridge and drop TURN relay range mapping
- Remove obsolete nginx restart handler; rely on 'docker compose up' notify
- Fix spreed task condition to use HPB standalone flag
- docker-compose.yml.j2: parameterize service names, use NEXTCLOUD_*_SERVICE vars, align host-gateway condition with HPB, tidy ports/expose/network blocks
- env.j2/nginx configs: rename TALK_* → HPB_* variables and locations; use templated NEXTCLOUD_SERVICE for php upstream
- vars: introduce entity_name; centralize *SERVICE keys; rename all Talk vars to HPB; adjust whiteboard keys; compute URLs/JSON configs accordingly
- spreed plugin vars: point to HPB signaling/STUN/TURN and internal secret

Ref: https://chatgpt.com/share/68db9f41-16ec-800f-9cdf-7530862f89aa

roles/web-app-nextcloud/tasks/01_fullstack.yml

@@ -27,11 +27,10 @@
     owner:  "{{ NEXTCLOUD_DOCKER_USER_id }}"
     group:  "{{ NEXTCLOUD_DOCKER_USER_id }}"
   loop:     "{{ lookup('fileglob', role_path ~ '/templates/config/*.j2', wantlist=True) }}"
-  # Not all type of changes take instantly place. Due to this reason a rebuild is required.
   notify: docker compose up
 
 - name: create internal nextcloud nginx configuration
   template:
     src:  "nginx/docker.conf.j2" 
     dest: "{{ NEXTCLOUD_HOST_NGINX_SRC }}"
-  notify: restart nextcloud nginx service
+  notify: docker compose up