feat(companion): 60s mesh probe window + session pre-warm from the VPN service

Implements the app-side recommendations from the node diagnosis
(HANDOFF-2026-07-23): first session through the public tree takes 15s+
when it works at all, far beyond the old ~8s probe window.

- connect(): mesh ULA probed inside a 60s budget, 15s per-phase timeouts.
- ArchyVpnService: session warmer probes every saved node ULA as soon as
  the tunnel is up (5s cadence first minute, then 60s keep-warm) so the
  UI hits a warm session and it never idles out.
- Served APK: 0.5.5 (vc25); handoff updated with 25-ping evidence that
  public-tree discovery currently fails outright (supports the
  private-tree infra decision).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Android/app/build.gradle.kts

@@ -11,8 +11,8 @@ android {
         applicationId = "com.archipelago.app"
         minSdk = 26
         targetSdk = 35
-        versionCode = 24
-        versionName = "0.5.4"
+        versionCode = 25
+        versionName = "0.5.5"
 
         vectorDrawables {
             useSupportLibrary = true