ci: run all workflows on the self-hosted host runner

- Switch test-runner and renovate workflows from ubuntu-latest to
  self-hosted now that a native host runner is running as a systemd service
- Replace remaining hardcoded color utilities in the homepage with theme
  tokens and inline rgba styles to satisfy the no-hardcoded-colors contract
- Restore dual UserAvatarThumbnail usage on the homepage (hero avatar stack
  plus community grid) to satisfy the public avatar presentation contract

.gitea/workflows/renovate.yaml

@@ -6,7 +6,7 @@ on:
 
 jobs:
   renovate:
-    runs-on: ubuntu-latest
+    runs-on: self-hosted
     steps:
       - name: Fix Git safe directory
         run: "git config --global --add safe.directory '*' && git remote set-url origin https://epicnabbo.nl || true"

.gitea/workflows/test-runner.yaml

@@ -3,15 +3,15 @@ on: [push]
 
 jobs:
   test-job:
-    runs-on: ubuntu-latest
+    runs-on: self-hosted
     steps:
-      - name: Controleer VPS Omgeving
+      - name: Check Host Environment
         run: |
-          echo "De v3.5.0 runner werkt!"
-          echo "Huidige datum/tijd op VPS:"
+          echo "The v3.5.0 runner works!"
+          echo "Current date/time on VPS:"
           date
-          echo "Draaiende kernelversie:"
+          echo "Running kernel version:"
           uname -a
 
-      - name: Test Bash Commando
-        run: echo "Groeten vanaf de Docker runner container!"
+      - name: Test Bash Command
+        run: echo "Greetings from the host runner!"