feat(proxy,bigbluebutton): use parameterized HTML location template & add build retry

- proxy(html.conf.j2):
  * Make proxy_pass more robust (strip '=', '^~' prefixes; ignore @/~ match locations)
  * Switch WS header to $connection_upgrade
  * Unify timeouts (proxy_connect_timeout 5s)
  * Lua optional: include only when proxy_lua_enabled=true; unset Accept-Encoding only then
  * Buffering via flag: proxy_buffering/proxy_request_buffering 'on' with Lua, otherwise 'off'
- proxy(media.conf.j2): minor formatting/spacing fix
- inj-css(head_sub.j2): consistent spacing for global_css_version
- bigbluebutton(tasks/main.yml):
  * Render HTML location block once before include_role (location='^~ /html5client', OAuth2/Lua disabled)
  * Pass rendered snippet via proxy_extra_configuration to the vHost
  * Cleanup afterwards: proxy_extra_configuration = undef()
- docker-compose(handlers):
  * Build with retry: if 'docker compose build' fails -> retry with '--no-cache --pull'
  * Enable BuildKit (DOCKER_BUILDKIT=1, COMPOSE_DOCKER_CLI_BUILD=1)
- vars: trailing newline / minor formatting

Motivation:
- BBB HTML5 client (^~ /html5client) needs a separate location without Lua/buffering.
- More resilient CI/CD builds via automatic no-cache retry.
- Cleaner headers/proxy defaults and fewer side effects.

Files:
- roles/docker-compose/handlers/main.yml
- roles/srv-proxy-7-4-core/templates/location/html.conf.j2
- roles/srv-proxy-7-4-core/templates/location/media.conf.j2
- roles/srv-web-7-7-inj-css/templates/head_sub.j2
- roles/web-app-bigbluebutton/tasks/main.yml
- roles/web-app-bigbluebutton/vars/main.yml

roles/web-app-bigbluebutton/tasks/main.yml

@@ -1,4 +1,14 @@
 ---
+- name: Render HTML-Location-Block in Variable
+  set_fact:
+    proxy_extra_configuration: >-
+      {{ lookup('ansible.builtin.template',
+                playbook_dir ~ '/roles/srv-proxy-7-4-core/templates/location/html.conf.j2') | trim }}
+  vars:
+    location: '^~ /html5client'
+    oauth2_proxy_enabled: false
+    proxy_lua_enabled: false
+
 - name: "load docker, proxy for '{{application_id}}'"
   include_role:
     name: cmp-docker-proxy
@@ -7,6 +17,10 @@
 - name: "include 04_seed-database-to-backup.yml"
   include_tasks: "{{ playbook_dir }}/roles/sys-bkp-docker-2-loc/tasks/04_seed-database-to-backup.yml"
 
+- name: "Unset 'proxy_extra_configuration'"
+  set_fact:
+    proxy_extra_configuration: "{{ undef() }}"
+
 - name: configure websocket_upgrade.conf
   copy: 
     src:  "websocket_upgrade.conf"