fix: replace generic exit 1 with specific exit codes in ct/ and install/ scripts (#12475)

Part of #12467 — scripts only (no framework changes).

New exit codes 250-254 registered in api.func and error_handler.func:
- 250: App download failed or version not determined
- 251: App file extraction failed (corrupt/incomplete archive)
- 252: App required file or resource not found
- 253: App data migration required — update aborted
- 254: App user declined prompt or input timed out

Existing codes reused where applicable:
- 10: privileged/Docker required (unifi-os-server)
- 64: invalid user input (postgresql, tomcat)
- 71: system error (pulse useradd)
- 150: service failed to start (docker, npmplus)
- 153: build failed (booklore)
- 233: app not installed (evcc, endurain, grafana, loki, itsm-ng)
- 236: hardware not detected (unifi-os-server /dev/net/tun)
- 238: OS not supported (frigate)

install/frigate-install.sh

@@ -17,7 +17,7 @@ update_os
 source /etc/os-release
 if [[ "$VERSION_ID" != "12" ]]; then
   msg_error "Frigate requires Debian 12 (Bookworm) due to Python 3.11 dependencies"
-  exit 1
+  exit 238
 fi
 
 msg_info "Converting APT sources to DEB822 format"