fix: 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/Projects.vue

@@ -104,13 +104,13 @@
 
           <!-- Hourly Rate -->
           <div>
-            <label class="block text-[0.6875rem] text-text-tertiary uppercase tracking-[0.08em] mb-1.5">Hourly Rate ($)</label>
+            <label class="block text-[0.6875rem] text-text-tertiary uppercase tracking-[0.08em] mb-1.5">Hourly Rate ({{ getCurrencySymbol() }})</label>
             <AppNumberInput
               v-model="formData.hourly_rate"
               :min="0"
               :step="1"
               :precision="2"
-              prefix="$"
+              :prefix="getCurrencySymbol()"
             />
           </div>
 
@@ -200,7 +200,7 @@ import AppSelect from '../components/AppSelect.vue'
 import { useProjectsStore, type Project } from '../stores/projects'
 import { useClientsStore } from '../stores/clients'
 import { useSettingsStore } from '../stores/settings'
-import { formatCurrency } from '../utils/locale'
+import { formatCurrency, getCurrencySymbol } from '../utils/locale'
 
 const colorPresets = ['#D97706', '#3B82F6', '#8B5CF6', '#EC4899', '#10B981', '#EF4444', '#06B6D4', '#6B7280']