feat: add transitions and micro-interactions across all views

- Page transitions with slide-up/fade on route changes (App.vue)
- NavRail sliding active indicator with spring-like easing
- List enter/leave/move animations on Entries, Projects, Clients, Timer
- Modal enter/leave transitions with scale+fade on all dialogs
- Dropdown transitions with overshoot on all select/picker components
- Button feedback (scale on hover/active), card hover lift effects
- Timer pulse on start, glow on stop, floating empty state icons
- Content fade-in on Dashboard, Reports, Calendar, Timesheet
- Tag chip enter/leave animations in AppTagInput
- Progress bar smooth width transitions
- Implementation plan document

src/components/NavRail.vue

@@ -34,6 +34,10 @@ const navItems = [
 
 const currentPath = computed(() => route.path)
 
+const activeIndex = computed(() => {
+  return navItems.findIndex(item => item.path === currentPath.value)
+})
+
 function navigate(path: string) {
   router.push(path)
 }
@@ -41,24 +45,25 @@ function navigate(path: string) {
 
 <template>
   <nav class="w-12 flex flex-col items-center bg-bg-surface border-r border-border-subtle shrink-0">
-    <!-- Navigation icons -->
-    <div class="flex-1 flex flex-col items-center pt-2 gap-1">
+    <div class="relative flex-1 flex flex-col items-center pt-2 gap-1">
+      <!-- Sliding active indicator -->
+      <div
+        v-if="activeIndex >= 0"
+        class="absolute left-0 w-[2px] bg-accent transition-all duration-300"
+        :style="{ top: `${activeIndex * 52 + 8 + 8}px`, height: '36px' }"
+        style="transition-timing-function: cubic-bezier(0.22, 1, 0.36, 1);"
+      />
+
       <button
         v-for="item in navItems"
         :key="item.path"
         @click="navigate(item.path)"
-        class="relative w-12 h-12 flex items-center justify-center transition-colors duration-150 group"
+        class="relative w-12 h-[52px] flex items-center justify-center transition-colors duration-150 group"
         :class="currentPath === item.path
           ? 'text-text-primary'
           : 'text-text-tertiary hover:text-text-secondary'"
         :title="item.name"
       >
-        <!-- Active indicator (left border) -->
-        <div
-          v-if="currentPath === item.path"
-          class="absolute left-0 top-2 bottom-2 w-[2px] bg-accent"
-        />
-
         <component :is="item.icon" class="w-[18px] h-[18px]" :stroke-width="1.5" />
 
         <!-- Tooltip -->