feat: Add var_gpu flag for GPU passthrough configuration (#9764)

* feat: Add var_gpu flag for GPU passthrough configuration

Changes:
- Add var_gpu variable to CT scripts for explicit GPU control
- Remove hardcoded GPU_APPS list - GPU detection now uses var_gpu flag
- Add var_gpu to VAR_WHITELIST for persistence in default.vars and app.vars
- Add GPU Passthrough option (Step 19) to advanced_settings wizard (now 20 steps)
- Update documentation

Apps with var_gpu=yes (GPU enabled by default):
- Media: jellyfin, plex, emby, channels, ersatztv, tunarr
- Transcoding: tdarr, unmanic, fileflows
- AI/ML: ollama, openwebui
- NVR: frigate, immich

Usage:
- Disable GPU: var_gpu=no bash -c '$(curl -fsSL ...jellyfin.sh)'
- Enable GPU: var_gpu=yes bash -c '$(curl -fsSL ...debian.sh)'
- Via default.vars: echo 'var_gpu=yes' >> /usr/local/community-scripts/default.vars
- Via advanced settings wizard (Step 19)

* fix: tput rmcup timing, GPU line indentation, echo_default GPU display

* style: add GPU icon variable for consistent formatting

ct/tdarr.sh

@@ -13,6 +13,7 @@ var_disk="${var_disk:-4}"
 var_os="${var_os:-debian}"
 var_version="${var_version:-13}"
 var_unprivileged="${var_unprivileged:-1}"
+var_gpu="${var_gpu:-yes}"
 
 header_info "$APP"
 variables