fix(openwrt): detect opkg silent failure and show disk space error

BusyBox opkg exits 0 even when 'Cannot install' due to insufficient space,
causing the fallback to silently report success. Now captures stderr and
checks for the failure string explicitly.

Adds user-visible error for the common case where the router flash is too
small for the TollGate package (~19 MB needed vs ~9 MB available on typical
budget routers). Adds error prefixes to the RPC sanitizer allowlist so the
message reaches the UI instead of showing 'Check server logs'.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

core/archipelago/src/api/rpc/middleware.rs

@@ -66,6 +66,9 @@ pub(super) fn sanitize_error_message(msg: &str) -> String {
         "Bitcoin address",
         "No router",
         "No OpenWrt",
+        "No space left",
+        "TollGate installation failed",
+        "No pre-built TollGate",
     ];
     for prefix in &user_facing_prefixes {
         if msg.starts_with(prefix) {