feat: Add data export/import functionality (#22)

* feat: add data export/import functionality

- Add /export and /import API endpoints with schema-independent JSON format
- Export includes: medications, dose history, settings, share links
- Uses _exportId references for medications, remapped on import
- Images exported as base64 data URLs
- Optional sensitive data inclusion (shoutrrr URLs, etc.)
- Import replaces all existing data with confirmation warning
- Add comprehensive test coverage
- Add English and German translations
- Add frontend UI in Settings page with export/import controls

* fix: correct JSX structure and TypeScript types

- Fix modal placement outside ternary expression in Settings
- Add type assertion for request.body in import route test

* docs: translate copilot-instructions to English

- Add explicit rule that English is the primary language
- Translate all German sections to English
- User may communicate in German, but all project artifacts must be English

backend/src/index.ts

@@ -19,6 +19,7 @@ import { settingsRoutes } from "./routes/settings.js";
 import { plannerRoutes } from "./routes/planner.js";
 import { shareRoutes } from "./routes/share.js";
 import { doseRoutes } from "./routes/doses.js";
+import { exportRoutes } from "./routes/export.js";
 import { startReminderScheduler } from "./services/reminder-scheduler.js";
 import { startIntakeReminderScheduler } from "./services/intake-reminder-scheduler.js";
 
@@ -113,6 +114,7 @@ export async function createApp(options?: {
   await app.register(plannerRoutes);
   await app.register(shareRoutes);
   await app.register(doseRoutes);
+  await app.register(exportRoutes);
 
   return app;
 }
@@ -181,6 +183,7 @@ await app.register(settingsRoutes);
 await app.register(plannerRoutes);
 await app.register(shareRoutes);
 await app.register(doseRoutes);
+await app.register(exportRoutes);
 
 const start = async () => {
   try {