fix: globe rendering, CPU sizing, manual location support

- Fix globe destroyed on re-render by preserving canvas DOM node across
  renderLocationCard() calls instead of recreating from scratch
- Reduce globe.gl camera minDistance (180->120) so globe is visible in
  200px container
- Clear stale globeInstance ref when canvas is gone
- Enlarge CPU gauge (90->110px), percentage label (18->22px), core bars
  (24->48px height), and detail text (11->12px)
- JS fetchLocation() now supplements server response with client-side
  ObserverLocation.getShared() from localStorage when server returns
  'default' or 'none', picking up manual coordinates from settings modal
- Location priority: GPS > config env vars > manual (localStorage) > default

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

static/css/modes/system.css

@@ -134,8 +134,8 @@
 
 .sys-gauge-arc {
     position: relative;
-    width: 90px;
-    height: 90px;
+    width: 110px;
+    height: 110px;
     flex-shrink: 0;
 }
 
@@ -168,7 +168,7 @@
     top: 50%;
     left: 50%;
     transform: translate(-50%, -50%);
-    font-size: 18px;
+    font-size: 22px;
     font-weight: 700;
     font-family: var(--font-mono, 'JetBrains Mono', monospace);
     color: var(--text-primary, #e0e0ff);
@@ -176,25 +176,25 @@
 
 .sys-gauge-details {
     flex: 1;
-    font-size: 11px;
+    font-size: 12px;
 }
 
 /* Per-core bars */
 .sys-core-bars {
     display: flex;
-    gap: 3px;
+    gap: 4px;
     align-items: flex-end;
-    height: 24px;
-    margin-top: 8px;
+    height: 48px;
+    margin-top: 12px;
 }
 
 .sys-core-bar {
     flex: 1;
     background: var(--bg-primary, #0d0d1a);
-    border-radius: 2px;
+    border-radius: 3px;
     position: relative;
-    min-width: 4px;
-    max-width: 16px;
+    min-width: 6px;
+    max-width: 32px;
     height: 100%;
 }