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/unifi-os-server-install.sh

@@ -16,13 +16,13 @@ update_os
 if [[ "${CTTYPE:-1}" != "0" ]]; then
   msg_error "UniFi OS Server requires a privileged LXC container."
   msg_error "Recreate the container with unprivileged=0."
-  exit 1
+  exit 10
 fi
 
 if [[ ! -e /dev/net/tun ]]; then
   msg_error "Missing /dev/net/tun in container."
   msg_error "Enable TUN/TAP (var_tun=yes) or add /dev/net/tun passthrough."
-  exit 1
+  exit 236
 fi
 
 msg_info "Installing dependencies"
@@ -48,7 +48,7 @@ TEMP_JSON="$(mktemp)"
 if ! curl -fsSL "$API_URL" -o "$TEMP_JSON"; then
   rm -f "$TEMP_JSON"
   msg_error "Failed to fetch data from Ubiquiti API"
-  exit 1
+  exit 250
 fi
 LATEST=$(jq -r '
   ._embedded.firmware
@@ -62,7 +62,7 @@ UOS_URL=$(echo "$LATEST" | jq -r '._links.data.href')
 rm -f "$TEMP_JSON"
 if [[ -z "$UOS_URL" || -z "$UOS_VERSION" || "$UOS_URL" == "null" ]]; then
   msg_error "Failed to parse UniFi OS Server version or download URL"
-  exit 1
+  exit 250
 fi
 msg_ok "Found UniFi OS Server ${UOS_VERSION}"