Add photo upload for PDQ Z-reports and receipt evidence

DB:
- Add attachment_type ('pdq_z_report' | 'receipt_error' | 'other') and
  label columns to cash_count_attachments; migrate existing rows via
  ALTER TABLE IF NOT EXISTS (no data loss)

Backend:
- Upload route now reads attachment_type and label from multipart form
  fields alongside the file, stores them in the DB

Frontend:
- PhotoUploader component: thumbnail grid, upload button (images + PDF),
  spinner during upload, ✕ delete button on each photo, click opens in
  new tab
- DailyCashUp: PDQ Z-Reports card (one section per machine — Front Desk /
  Restaurant Bar) appears after Card Machines when a cash up exists
- DailyCashUp: Receipt Evidence card at bottom for any discrepancy photos;
  stays editable even on final cash ups so receipts can be added later

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/types.ts

@@ -82,6 +82,8 @@ export interface Attachment {
   file_size: number
   mime_type: string
   uploaded_at: string
+  attachment_type: 'pdq_z_report' | 'receipt_error' | 'other'
+  label: string | null
 }
 
 export interface FloatCount {