feat(inbounds): expose Vision testseed field with sensible default

Add a "Vision testseed" form item to the inbound modal for TCP + TLS/reality
inbounds, normalized to positive integers and defaulting to [900,500,900,256].
Apply the same default in the outbound form adapter when no valid saved seed
is present.

Replace the http/mixed snapshot assertions in inbound-defaults with explicit
field checks so generated credentials don't break the snapshots.

frontend/src/lib/xray/outbound-form-adapter.ts

@@ -116,7 +116,7 @@ function vlessFromWire(raw: Raw): VlessOutboundFormSettings {
   const testseed = savedSeed.length === 4
     && savedSeed.every((n) => Number.isInteger(n) && (n as number) > 0)
     ? (savedSeed as number[])
-    : [];
+    : [900, 500, 900, 256];
   return {
     address,
     port,