feat(earth): toolbar and zoom improvements

- Add box-sizing/padding normalization to toolbar buttons
- Remove zoom slider, implement click/hold zoom behavior (+/- buttons)
- Add 10% step on click, 1% continuous on hold
- Fix satellite init: show satellite points immediately, delay trail visibility
- Fix breathing effect: faster pulse, wider opacity range
- Add toggle-cables functionality with visibility state
- Initialize satellites and cables as visible by default

frontend/public/earth/css/base.css

@@ -43,7 +43,7 @@ body {
   display: flex;
   flex-direction: column;
   align-items: center;
-  gap: 4px;
+  gap: 6px;
   background: rgba(10, 10, 30, 0.9);
   padding: 8px 4px;
   border-radius: 24px;
@@ -93,7 +93,9 @@ body {
   justify-content: center;
   transition: all 0.2s ease;
   padding: 0;
+  margin: 0;
   flex: 0 0 auto;
+  box-sizing: border-box;
 }
 
 #zoom-toolbar .zoom-btn:hover {
@@ -306,6 +308,9 @@ input[type="range"]::-webkit-slider-thumb {
   align-items: center;
   justify-content: center;
   transition: all 0.2s ease;
+  box-sizing: border-box;
+  padding: 0;
+  margin: 0;
 }
 
 .toolbar-btn:hover {