catalog: repoint HDD_PATH defaults/placeholders to /mnt/felhom-drives/<name>

Intermediary-mount re-architecture: drives are visible in-guest at the stable
/mnt/felhom-drives/<name>. Composes already use ${HDD_PATH}/${USERDATA_PATH}
(injected + repointed by controller v0.67.0); this updates the UI placeholders,
templates.json defaults, and doc/script examples to the new convention.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

scripts/generate-customer.sh

@@ -11,7 +11,7 @@
 #
 #  Usage:
 #    ./scripts/generate-customer.sh --customer demo-felhom --domain demo-felhom.eu \
-#        --hdd-path /mnt/hdd_1 --push
+#        --hdd-path /mnt/felhom-drives/hdd_1 --push
 #
 #  Version: 1.0.0
 #===============================================================================
@@ -110,7 +110,7 @@ REQUIRED:
     --domain DOMAIN     Customer domain (e.g., demo-felhom.eu)
 
 OPTIONAL:
-    --hdd-path PATH     External HDD mount path (e.g., /mnt/hdd_1)
+    --hdd-path PATH     External HDD mount path (e.g., /mnt/felhom-drives/hdd_1)
                         If omitted, apps needing HDD show a field in Portainer.
     --apps LIST         Comma-separated app list (default: all available)
                         Available: actualbudget,docmost,filebrowser,homebox,
@@ -135,7 +135,7 @@ OUTPUT:
 EXAMPLES:
     # All apps, with HDD
     ./scripts/generate-customer.sh --customer demo-felhom \
-        --domain demo-felhom.eu --hdd-path /mnt/hdd_1 --push
+        --domain demo-felhom.eu --hdd-path /mnt/felhom-drives/hdd_1 --push
 
     # Raspberry Pi — lightweight apps only
     ./scripts/generate-customer.sh --customer pi-customer-1 \