feat(clients): reachability-probed presence + shareable Decky host management

Add a bounded, trust-agnostic, mDNS-INDEPENDENT QUIC reachability probe and
surface it everywhere saved-host presence is shown, so a host reached over a
routed network (Tailscale/VPN/multicast-filtering LAN) no longer reads Offline
just because it isn't advertising — the display-side companion to the 0.8.4
dial-first connect fix.

Core:
- punktfunk-core: NativeClient::probe (bounded handshake; a real host answers even
  on trust mismatch, a wrong/closed/TCP-only port fails) + punktfunk_probe C ABI
  (ABI_VERSION 3->4, header regenerated).
- pf-client-core: trust::probe_reachable_many (parallel per-host sweep).

Presence pips now read `advertising OR probed-reachable`, refreshed by a ~10-12s
background sweep off the UI thread:
- Linux (relm4): ui_hosts probed map + HostsMsg::Probed sweep.
- Windows (windows-reactor): pf-probe worker -> HostsProps.probed.
- Apple (SwiftUI): HostStore.refreshReachability, driven by HomeView + GamepadHomeView .task.
- Android (Compose): nativeProbe JNI seam + periodic LaunchedEffect (LNP-gated),
  online dot added to the touch HostCard.
- Decky already probes via --list-hosts --probe.

Decky client: make the flatpak client's known-hosts store the single source of
truth via new headless CLI modes (--list-hosts / --add-host / --set-host /
--forget-host / --reset / --reachable). The plugin can now add a host by address,
edit/forget hosts, reset all state (keeping the client identity), and shows
probe-backed online pips — state is shared with the desktop client, not duplicated.

Also lands in-progress Android 17 LNP groundwork (targetSdk 37 +
ACCESS_LOCAL_NETWORK runtime flow, permission dialogs) that was already present in
the working tree.

Verified: cargo check + clippy clean (punktfunk-core, pf-client-core, linux,
android native); android assembleDebug BUILD SUCCESSFUL; decky typecheck + rollup
build clean; probe true/false-positive behaviour exercised against a live host.
Windows and Apple were not compiled locally (no MSVC/Xcode on this Linux box).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

clients/android/app/build.gradle.kts

@@ -11,7 +11,7 @@ plugins {
 
 android {
     namespace = "io.unom.punktfunk"
-    compileSdk = 37 // Android 17 — required by androidx.core 1.19.0; targetSdk stays 36 for now.
+    compileSdk = 37 // Android 17 — required by androidx.core 1.19.0.
 
     defaultConfig {
         // Load from .env if it exists (local dev), otherwise from System.getenv (CI)
@@ -26,7 +26,11 @@ android {
         // the handful of API 31+ APIs we use are runtime-gated (Material You → brand palette, rumble
         // → legacy Vibrator, NEARBY_WIFI/lights/ADPF already gated), so nothing is lost above 28.
         minSdk = 28
-        targetSdk = 36
+        // Android 17: targeting 37 makes Local Network Protection MANDATORY — all LAN traffic (the
+        // QUIC dial, mDNS, WoL, the library fetch) is blocked until the user grants the
+        // ACCESS_LOCAL_NETWORK runtime permission. ConnectScreen owns that request/rationale flow;
+        // don't bump past 37 without re-checking the next release's behavior changes.
+        targetSdk = 37
         val vCode = (props.getProperty("VERSION_CODE") ?: System.getenv("VERSION_CODE"))
         versionCode = vCode?.toInt() ?: 1
         // versionName is the single project version, threaded from CI (a vX.Y.Z release or a