Refactor: migrate cmp/* and srv/* roles into sys-stk/* and sys-svc/* namespaces

- Removed obsolete 'cmp' category, introduced 'stk' category (fa-bars-staggered icon).
- Renamed roles:
  * cmp-db-docker → sys-stk-back-stateful
  * cmp-docker-oauth2 → sys-stk-back-stateless
  * srv-domain-provision → sys-stk-front
  * cmp-db-docker-proxy → sys-stk-full-stateful
  * cmp-docker-proxy → sys-stk-full-stateless
  * cmp-rdbms → sys-svc-rdbms
- Updated all include_role references, vars, templates and README.md files.
- Adjusted run_once comments and variable paths accordingly.
- Updated all web-app roles to use new sys-stk/* and sys-svc/* roles.

Conversation: https://chatgpt.com/share/68b0ba66-09f8-800f-86fc-76c47009d431

roles/categories.yml

@@ -1,9 +1,4 @@
 roles:
-  cmp:
-    title: "Compositions"
-    description: "Composition of other roles."
-    icon: "fas fa-sitemap"
-    invokable: false
   docker:
     title: "Docker Toolkit"
     description: "Generic Docker helpers and utilities (compose wrappers, container tooling)."
@@ -56,6 +51,11 @@ roles:
       description: "DNS providers, records, and rDNS management (Cloudflare, Hetzner, etc.)."
       icon: "fas fa-network-wired"
       invokable: false
+    stk:
+      title: "Stack"
+      description: "Stack levels to setup the server"
+      icon: "fas fa-bars-staggered"
+      invokable: false
   update:
     title: "Updates & Package Management"
     description: "OS & package updates"