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/docker-compose/handlers/main.yml

@@ -11,14 +11,23 @@
     - docker compose restart
     - docker compose just up
 
-- name: Build docker 
-  command:
-    cmd:   docker compose build
+- name: Build docker compose 
+  shell: |
+    set -euo pipefail
+    docker compose build || { 
+      echo "Retrying without cache and pulling bases...";
+      docker compose build --no-cache --pull; 
+    }
+  args:
     chdir: "{{ docker_compose.directories.instance }}"
+    executable: /bin/bash
   environment:
     COMPOSE_HTTP_TIMEOUT: 600
     DOCKER_CLIENT_TIMEOUT: 600
-  listen: 
+    # Faster build
+    DOCKER_BUILDKIT: "1"
+    COMPOSE_DOCKER_CLI_BUILD: "1"
+  listen:
     - docker compose build
 
 - name: docker compose up