Combine scan+receipts into one flow, add plausibility check,

photo viewing, and record drill-down

- Overview is now the single front page (list + "+" FAB to scan)
  instead of a separate near-empty Scan tab; export moved from
  Overview into the drawer
- Drop petrol_station/transaction_number from storage, the edit
  form, and CSV/ODS export - not useful for a personal fuel-cost log
  (destructive Room migration, version 1->2 already shipped earlier)
- Add a live plausibility check (total_price vs. price_per_litre *
  litres - discount) shown as a green/red badge on the review screen
- Add a shared Details/Photo review screen (ReceiptReviewScreen),
  with pinch-to-zoom on the photo (new Coil dependency), reused both
  right after a scan and when drilling into an already-saved receipt
  from the list (ReceiptDetailScreen, with Update/Delete)
- Fix receipt photos not surviving an app restart: camera/gallery
  captures now write to internal storage (filesDir) instead of the
  cache dir, which the OS can clear independent of the database; the
  gallery picker was also saving the Photo Picker's own short-lived
  content:// Uri instead of a Uri onto our persisted copy
- App log: add a Copy button and selectable text
- Fix the connection status bar overlapping the system gesture nav
  bar under edge-to-edge
- Settings: prefill an editable example server URL, add a "Test
  connection" button; both it and the connection status bar now
  surface the actual failure reason, not just pass/fail

android/app/src/main/res/values/strings.xml

@@ -6,6 +6,7 @@
     <string name="nav_overview">Receipts</string>
     <string name="nav_settings">Settings</string>
     <string name="nav_log">App log</string>
+    <string name="nav_back">Back</string>
 
     <string name="capture_take_photo">Take photo</string>
     <string name="capture_choose_gallery">Choose from gallery</string>
@@ -16,8 +17,6 @@
     <string name="capture_stage_error">Something went wrong: %1$s</string>
     <string name="capture_retry">Retry</string>
     <string name="capture_save">Save</string>
-    <string name="capture_field_petrol_station">Petrol station</string>
-    <string name="capture_field_transaction_number">Transaction number</string>
     <string name="capture_field_date">Date (DD.MM.YYYY)</string>
     <string name="capture_field_time">Time (HH:MM:SS)</string>
     <string name="capture_field_price_per_litre">Price per litre</string>
@@ -25,9 +24,18 @@
     <string name="capture_field_discount">Discount</string>
     <string name="capture_field_total_price">Total price</string>
 
+    <string name="receipt_tab_details">Details</string>
+    <string name="receipt_tab_photo">Photo</string>
+    <string name="receipt_no_photo">No photo available</string>
+    <string name="receipt_photo_missing">Photo file is missing</string>
+    <string name="receipt_scan_ok">Scan OK</string>
+    <string name="receipt_scan_dubious">Scan dubious</string>
+    <string name="receipt_update">Update</string>
+    <string name="receipt_delete">Delete</string>
+
     <string name="overview_empty">No receipts have been scanned yet</string>
     <string name="overview_column_date">Date</string>
-    <string name="overview_column_station">Station</string>
+    <string name="overview_column_litres">Litres</string>
     <string name="overview_column_total">Total</string>
     <string name="overview_delete">Delete</string>
     <string name="overview_export_csv">Export CSV</string>
@@ -46,6 +54,7 @@
     <string name="status_not_configured">No server configured - see Settings</string>
     <string name="status_checking">Checking connection…</string>
 
+    <string name="log_copy">Copy log</string>
     <string name="log_clear">Clear log</string>
     <string name="log_empty">Nothing logged yet</string>
 </resources>