dynamic currency symbols and integrated datetime picker

- Replace all hardcoded prefix="$" with :prefix="getCurrencySymbol()"
  in Settings, Projects, and Invoices views
- Replace hardcoded ($) labels with dynamic currency symbol
- Extend AppDatePicker with showTime prop + hour/minute v-models
  for integrated date+time selection
- Simplify Entries.vue to use single AppDatePicker with showTime
  instead of separate hour/minute inputs

src/views/Entries.vue

@@ -166,31 +166,13 @@
           <!-- Start Date & Time -->
           <div>
             <label class="block text-[0.6875rem] text-text-tertiary uppercase tracking-[0.08em] mb-1.5">Start Date & Time</label>
-            <div class="flex items-center gap-2">
-              <div class="flex-1">
-                <AppDatePicker
-                  v-model="editDate"
-                  placeholder="Date"
-                />
-              </div>
-              <div class="flex items-center gap-1">
-                <input
-                  v-model="editHour"
-                  type="number"
-                  min="0"
-                  max="23"
-                  class="w-12 px-2 py-2 bg-bg-inset border border-border-subtle rounded-lg text-[0.8125rem] text-text-primary text-center font-mono focus:outline-none focus:border-border-visible [appearance:textfield] [&::-webkit-outer-spin-button]:appearance-none [&::-webkit-inner-spin-button]:appearance-none"
-                />
-                <span class="text-text-tertiary text-sm font-mono">:</span>
-                <input
-                  v-model="editMinute"
-                  type="number"
-                  min="0"
-                  max="59"
-                  class="w-12 px-2 py-2 bg-bg-inset border border-border-subtle rounded-lg text-[0.8125rem] text-text-primary text-center font-mono focus:outline-none focus:border-border-visible [appearance:textfield] [&::-webkit-outer-spin-button]:appearance-none [&::-webkit-inner-spin-button]:appearance-none"
-                />
-              </div>
-            </div>
+            <AppDatePicker
+              v-model="editDate"
+              :show-time="true"
+              v-model:hour="editHour"
+              v-model:minute="editMinute"
+              placeholder="Date & Time"
+            />
           </div>
 
           <!-- Buttons -->