feat: add graticule toggle control to all Leaflet maps

Adds a bottomleft grid button (MapUtils.addGraticuleControl) to every
map in the app — Meshtastic, MeshCore, Drone, SSTV/ISS, BT Locate,
WebSDR, and Weather Satellite — defaulting to visible. The weather
satellite map's bespoke addStyledGridOverlay() is removed in favour of
the shared implementation. Also updates map-utils.css with button
styles and map-utils.js with the new addGraticuleControl() method.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

static/js/modes/meshtastic.js

@@ -16,9 +16,9 @@ const Meshtastic = (function() {
 
     // Map state
     let meshMap = null;
-    let meshMarkers = {};  // nodeId -> marker
-    let localNodeId = null;
-    let clickDelegationAttached = false;
+    let meshMarkers = {};  // nodeId -> marker
+    let localNodeId = null;
+    let clickDelegationAttached = false;
 
     /**
      * Initialize the Meshtastic mode
@@ -33,14 +33,14 @@ const Meshtastic = (function() {
     /**
      * Setup event delegation for dynamically created elements
      */
-    function setupEventDelegation() {
-        if (clickDelegationAttached) return;
-        clickDelegationAttached = true;
-
-        // Handle button clicks in Leaflet popups and elsewhere
-        document.addEventListener('click', function(e) {
-            const tracerouteBtn = e.target.closest('.mesh-traceroute-btn');
-            if (tracerouteBtn) {
+    function setupEventDelegation() {
+        if (clickDelegationAttached) return;
+        clickDelegationAttached = true;
+
+        // Handle button clicks in Leaflet popups and elsewhere
+        document.addEventListener('click', function(e) {
+            const tracerouteBtn = e.target.closest('.mesh-traceroute-btn');
+            if (tracerouteBtn) {
                 const nodeId = tracerouteBtn.dataset.nodeId;
                 if (nodeId) {
                     sendTraceroute(nodeId);
@@ -137,6 +137,8 @@ const Meshtastic = (function() {
             }
         }
 
+        if (typeof MapUtils !== 'undefined') MapUtils.addGraticuleControl(meshMap);
+
         // Handle resize
         setTimeout(() => {
             if (meshMap) meshMap.invalidateSize();