Fix Settings modal crash: send licenseId as string, not Uint8Array

The Keysat client's payload exposes both:
  • licenseId    — raw 16-byte UUID as Uint8Array
  • licenseUuid  — same value, canonical string form

server/license.js was sending licenseId (the Uint8Array). After JSON
serialization that turned into an object like {"0":1,"1":2,...} on
the wire. The frontend's renderLicenseBlock() calls
`lic.licenseId.slice(0, 8)` to abbreviate the ID for display — .slice
doesn't exist on that object, so the template threw, the
app.innerHTML assignment silently aborted, and clicking the gear
looked like a no-op.

The render error guard added in 0.1.17 caught it on first repro:
  Render error: lic.licenseId.slice is not a function

Fix: switch to payload.licenseUuid (the string form).

server/license.js

@@ -162,7 +162,10 @@ export function checkLicense() {
     }
     base = emptyState({
       state: "licensed",
-      licenseId: payload.licenseId || null,
+      // payload.licenseId is a Uint8Array (raw 16-byte UUID); the canonical
+      // string form is licenseUuid. The frontend treats licenseId as a
+      // string (calls .slice on it), so always send the string here.
+      licenseId: payload.licenseUuid || null,
       entitlements: new Set(payload.entitlements || []),
       expiresAt: payload.expiresAt ? new Date(payload.expiresAt * 1000) : null,
       isTrial: !!(payload.flags & 1),