4K: download clients (packaged, idempotent) + Homepage tiles

Add SABnzbd+Transmission to radarr-4k/sonarr-4k with distinct categories (sabnzbd
movies-4k/tv-4k, transmission radarr-uhd/sonarr-uhd; Transmission forbids digits) so
they dont cross-import the 1080p instances. Packaged into deploy-arrs-4k.yml via an
idempotent ensure-arrs-4k-dl.py (changed=0). Homepage Radarr 4K/Sonarr 4K tiles
(HOMEPAGE_VAR keys, siteMonitor). 4K path proven: Obsession routed to radarr-4k,
grabbed WEBDL-2160p, 1080p rejected 'not wanted in profile'. Keys via vault, no secrets.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

homepage/services.yaml

@@ -55,6 +55,25 @@
           type: radarr
           url: http://radarr:7878
           key: {{HOMEPAGE_VAR_RADARR_KEY}}
+    - Radarr 4K:
+        icon: radarr.png
+        href: https://radarr-4k.goattw.net
+        description: 4K Movies (quality-first)
+        siteMonitor: https://radarr-4k.goattw.net
+        widget:
+          type: radarr
+          url: http://radarr-4k:7878
+          key: {{HOMEPAGE_VAR_RADARR4K_KEY}}
+
+    - Sonarr 4K:
+        icon: sonarr.png
+        href: https://sonarr-4k.goattw.net
+        description: 4K TV (quality-first)
+        siteMonitor: https://sonarr-4k.goattw.net
+        widget:
+          type: sonarr
+          url: http://sonarr-4k:8989
+          key: {{HOMEPAGE_VAR_SONARR4K_KEY}}
 
     - Prowlarr:
         icon: prowlarr.png