refactor(frontend): modularize App.tsx into components, pages, hooks, and context (#60)

- Extract App.tsx from 764 lines to ~404 lines
- Create reusable components: MedDetailModal, MobileEditModal, ShareDialog, etc.
- Add AppContext for global state management
- Split pages: DashboardPage, MedicationsPage, SchedulePage, SettingsPage, PlannerPage
- Create custom hooks: useAuth, useMedications, useSettings, useDoses, useSchedule
- Add utility functions in separate modules
- Fix stock status logic (>30 days = green/normal)
- Fix reminder threshold calculation (use reminderDaysBefore not lowStockDays)
- Fix takenBy validation (send [] instead of null)
- Fix datetime format for blister start times (add Z suffix)
- Style 'All OK' status as green/bold

BREAKING: None - all existing functionality preserved

frontend/src/i18n/de.json

@@ -50,8 +50,9 @@
     "reminders": {
       "active": "Automatische Erinnerungen aktiv",
       "allStockOk": "Bestand OK",
-      "allOk": "Alles OK",
+      "allOk": "✓ Alles OK",
       "lastReminder": "Letzte Erinnerung",
+      "next": "Nächste",
       "nextIn": "Nächste",
       "inDays": "in {{days}} Tagen",
       "noRemindersNeeded": "keine Erinnerungen nötig",
@@ -243,8 +244,8 @@
     "highStock": "Hoch",
     "noSchedule": "Kein Zeitplan",
     "enough": "Ausreichend",
-    "noPillsLeft": "⚠ Keine Tabletten mehr",
-    "stockOk": "✓ Bestand OK"
+    "noPillsLeft": "Keine Tabletten mehr",
+    "stockOk": "Bestand OK"
   },
   "tooltips": {
     "intakeReminders": "Einnahme-Erinnerungen aktiviert",

frontend/src/i18n/en.json

@@ -52,8 +52,9 @@
     "reminders": {
       "active": "Automatic reminders active",
       "allStockOk": "All stock OK",
-      "allOk": "All OK",
+      "allOk": "✓ All OK",
       "lastReminder": "Last reminder",
+      "next": "Next",
       "nextIn": "Next",
       "inDays": "in {{days}} days",
       "noRemindersNeeded": "no reminders needed",
@@ -245,8 +246,8 @@
     "highStock": "High",
     "noSchedule": "No Schedule",
     "enough": "Enough",
-    "noPillsLeft": "⚠ No pills left",
-    "stockOk": "✓ Stock OK"
+    "noPillsLeft": "No pills left",
+    "stockOk": "Stock OK"
   },
   "tooltips": {
     "intakeReminders": "Intake reminders enabled",