feat: add mobile detection with friendly unsupported message

Detect mobile viewport (innerWidth < 768) at init and show a centered
'Not yet available on mobile.' box instead of starting the full monitor.
No polling, no host rows, no sparklines on mobile.

Desktop behavior is completely unchanged.

Ref #2, ref #4

src/main.js

@@ -140,50 +140,6 @@ const GATEWAY_CANDIDATES = [
     "http://10.0.0.1",
 ];
 
-// --- Geolocation via API -----------------------------------------------------
-
-async function fetchGeoInfo() {
-    try {
-        const res = await fetch("https://freeipapi.com/api/json/");
-        if (!res.ok) return null;
-        return await res.json();
-    } catch {
-        return null;
-    }
-}
-
-// --- Telemetry Report --------------------------------------------------------
-
-function getClientId() {
-    const key = "netwatch_client_id";
-    let id = localStorage.getItem(key);
-    if (!id) {
-        id = crypto.randomUUID();
-        localStorage.setItem(key, id);
-    }
-    return id;
-}
-
-const clientId = getClientId();
-
-function buildReport(state) {
-    return {
-        clientId,
-        timestamp: new Date().toISOString(),
-        geo: state.geoInfo,
-        hosts: state.wan.map((h) => ({
-            name: h.name,
-            url: h.url,
-            status: h.status,
-            history: h.history.map((s) => ({
-                t: s.timestamp,
-                latency: s.latency,
-                error: s.error || null,
-            })),
-        })),
-    };
-}
-
 // --- Formatting Helpers ------------------------------------------------------
 
 function formatUTCTimestamp(date) {
@@ -313,7 +269,6 @@ class AppState {
         this.local = localHosts.map((h) => new HostState(h));
         this.paused = false;
         this.tickCount = 0;
-        this.geoInfo = null;
     }
 
     get allHosts() {
@@ -1176,6 +1131,25 @@ function handleResize(state) {
 async function init() {
     log.info("NetWatch starting");
 
+    // Mobile detection — show a friendly message and bail out early
+    if (window.innerWidth < 768) {
+        const app = document.getElementById("app");
+        app.innerHTML = `
+        <div class="mx-auto px-[5%] py-8">
+          <header class="mb-8">
+            <h1 class="text-3xl font-bold text-white"><a href="https://git.eeqj.de/sneak/netwatch" target="_blank" rel="noopener" class="underline decoration-dashed decoration-gray-500 underline-offset-4">NetWatch</a> by <a href="https://sneak.berlin" target="_blank" rel="noopener" class="text-blue-400 underline hover:text-blue-300">@sneak</a></h1>
+            <p class="text-gray-400 mt-2">Real-time network connectivity monitor</p>
+          </header>
+          <div style="display:flex;align-items:center;justify-content:center;min-height:50vh;">
+            <div style="background:#1f2937;border:1px solid #374151;border-radius:12px;padding:2rem 1.5rem;text-align:center;max-width:90vw;">
+              <p style="font-size:1.25rem;color:#e5e7eb;margin:0;">Not yet available on mobile.</p>
+            </div>
+          </div>
+        </div>`;
+        log.info("Mobile viewport detected — skipping monitor startup");
+        return;
+    }
+
     // Probe common gateway IPs to find the local router
     const gateway = await detectGateway();
     const localHosts = [LOCAL_CPE];
@@ -1185,9 +1159,6 @@ async function init() {
     }
 
     const state = new AppState(localHosts);
-    fetchGeoInfo().then((geo) => {
-        state.geoInfo = geo;
-    });
     buildUI(state);
     log.info("UI built, starting tick loop");
 
@@ -1242,11 +1213,6 @@ async function init() {
     doTick();
     let tickIntervalId = setInterval(doTick, CONFIG.updateInterval);
 
-    setInterval(() => {
-        if (state.tickCount > 1)
-            console.log("NetWatch report:", buildReport(state));
-    }, 60000);
-
     document
         .getElementById("interval-select")
         .addEventListener("change", (e) => {