feat: UI improvements and Space category

- Add new "Space" category with Satellite and ISS SSTV modes
- Rename "Scanner" to "Listening Post"
- SSTV now uses global SDR device selector
- Meshtastic map markers more visible (stronger glow, larger size)
- CSS layout fixes using flex instead of fixed heights

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

static/css/index.css

@@ -1769,8 +1769,7 @@ header h1 .tagline {
     font-family: 'JetBrains Mono', monospace;
     font-size: 11px;
     background: var(--bg-primary);
-    min-height: 400px;
-    max-height: 600px;
+    min-height: 0; /* Allow shrinking in flex context */
 }
 
 .output-content::-webkit-scrollbar {
@@ -2516,9 +2515,8 @@ header h1 .tagline {
 /* Satellite Dashboard Embed */
 .satellite-dashboard-embed {
     width: 100%;
-    height: calc(100vh - 200px);
-    min-height: 700px;
-    max-height: 900px;
+    flex: 1;
+    min-height: 400px;
     background: var(--bg-primary);
     border-radius: 8px;
     overflow: hidden;
@@ -3322,8 +3320,8 @@ header h1 .tagline {
     background: var(--bg-secondary);
     margin: 0 15px 10px 15px;
     border: 1px solid var(--border-color);
-    height: calc(100vh - 200px);
-    min-height: 400px;
+    flex: 1;
+    min-height: 0; /* Allow shrinking in flex context */
     box-sizing: border-box;
     overflow: hidden;
 }
@@ -3799,8 +3797,8 @@ header h1 .tagline {
 
 @media (max-width: 1200px) {
     .wifi-layout-container {
-        height: auto;
-        max-height: calc(100vh - 200px);
+        flex: 1;
+        min-height: 0;
     }
 
     .wifi-main-content {
@@ -3836,8 +3834,8 @@ header h1 .tagline {
     background: var(--bg-secondary);
     margin: 0 15px 10px 15px;
     border: 1px solid var(--border-color);
-    height: calc(100vh - 200px);
-    min-height: 400px;
+    flex: 1;
+    min-height: 0; /* Allow shrinking in flex context */
 }
 
 .bt-visuals-column {
@@ -4518,8 +4516,8 @@ header h1 .tagline {
 @media (max-width: 1200px) {
     .bt-layout-container {
         flex-direction: column;
-        height: auto;
-        max-height: calc(100vh - 200px);
+        flex: 1;
+        min-height: 0;
     }
 
     .bt-layout-container .wifi-visuals {

static/css/modes/meshtastic.css

@@ -420,6 +420,12 @@
     background: var(--bg-primary);
 }
 
+/* Override Leaflet's default div-icon styling for mesh markers */
+.mesh-marker-wrapper.leaflet-div-icon {
+    background: transparent;
+    border: none;
+}
+
 .mesh-map .leaflet-popup-content-wrapper {
     background: var(--bg-card);
     color: var(--text-primary);
@@ -437,37 +443,42 @@
     margin: 10px 12px;
 }
 
-/* Custom node marker */
+/* Custom node marker - high visibility on dark maps */
 .mesh-node-marker {
     display: flex;
     align-items: center;
     justify-content: center;
-    width: 28px;
-    height: 28px;
-    background: var(--accent-cyan);
-    border: 2px solid #fff;
+    width: 32px;
+    height: 32px;
+    background: #00ffff;  /* Bright cyan for maximum visibility */
+    border: 3px solid #ffffff;
     border-radius: 50%;
     box-shadow:
-        0 2px 6px rgba(0, 0, 0, 0.4),
-        0 0 12px 4px rgba(0, 212, 255, 0.5);  /* Cyan glow */
+        0 2px 8px rgba(0, 0, 0, 0.6),
+        0 0 20px 8px rgba(0, 255, 255, 0.7),  /* Strong outer glow */
+        inset 0 0 8px rgba(255, 255, 255, 0.3);  /* Inner highlight */
     color: #000;
     font-family: 'JetBrains Mono', monospace;
-    font-size: 10px;
+    font-size: 11px;
     font-weight: bold;
     text-shadow: 0 0 2px rgba(255, 255, 255, 0.8);
 }
 
 .mesh-node-marker.local {
-    background: var(--accent-green);
+    background: #00ff88;  /* Bright green for local node */
     box-shadow:
-        0 2px 6px rgba(0, 0, 0, 0.4),
-        0 0 12px 4px rgba(34, 197, 94, 0.5);  /* Green glow */
+        0 2px 8px rgba(0, 0, 0, 0.6),
+        0 0 20px 8px rgba(0, 255, 136, 0.7),  /* Strong green glow */
+        inset 0 0 8px rgba(255, 255, 255, 0.3);
 }
 
 .mesh-node-marker.stale {
-    background: var(--text-dim);
-    opacity: 0.7;
-    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.4);  /* No glow for stale */
+    background: #888888;
+    border-color: #aaaaaa;
+    opacity: 0.8;
+    box-shadow:
+        0 2px 6px rgba(0, 0, 0, 0.4),
+        0 0 8px 2px rgba(136, 136, 136, 0.3);  /* Subtle glow for stale */
 }
 
 /* ============================================