Tighten TimeSpinner spacing and fix build warnings

Reduce gap between numbers and h/m unit labels in the workday
schedule spinners. Remove unused parse_hour function and fix
Svelte state_referenced_locally warning in BreakScreen.

src/lib/components/BreakScreen.svelte

@@ -13,7 +13,7 @@
 
   let { standalone = false }: Props = $props();
 
-  const appWindow = standalone ? getCurrentWebviewWindow() : null;
+  const appWindow = $derived(standalone ? getCurrentWebviewWindow() : null);
 
   let currentActivity = $state<BreakActivity>(pickRandomActivity());
   let activityCycleTimer: ReturnType<typeof setInterval> | null = null;

src/lib/components/TimeSpinner.svelte

@@ -324,14 +324,14 @@
   .time-spinner {
     display: inline-flex;
     align-items: center;
-    gap: 4px;
+    gap: 2px;
     user-select: none;
     touch-action: none;
   }
 
   .wheel-field {
     position: relative;
-    width: 50px;
+    width: 44px;
     height: 36px;
     border-radius: 8px;
     background: rgba(255, 255, 255, 0.05);
@@ -376,13 +376,13 @@
     line-height: 1;
     backface-visibility: hidden;
     pointer-events: none;
-    padding-right: 12px;
+    padding-right: 6px;
   }
 
   /* Unit label pinned to the right of the field */
   .unit-badge {
     position: absolute;
-    right: 5px;
+    right: 3px;
     top: 50%;
     transform: translateY(-50%);
     font-size: 10px;