feat(data-entry): Bulk Receipt Upload cu Mobile UX Android Nativ

## Funcționalități Principale

### Bulk Upload & Processing
- Drag & drop pentru upload bonuri multiple oriunde pe pagină
- Batch processing cu job queue și worker pool
- Real-time updates via SSE (Server-Sent Events) cu fallback polling
- Duplicate detection via SHA-256 file hash
- Auto-retry pentru job-uri failed
- Cancel individual jobs sau batch complet

### Mobile UX - Android Native Style
- Top bar fixă cu hamburger, titlu centrat, acțiuni (search/filter)
- Bottom navigation cu 4 tab-uri (Bonuri, Upload, Rapoarte, Setări)
- FAB (Floating Action Button) cu hide/show on scroll
- Filter chips orizontal scrollabile
- Selecție multiplă prin long-press (500ms)
- Select All + Bulk Delete cu confirmare
- Layout Android pentru Create/Edit/View bon (Gmail compose style)

### Bug Fixes
- Refresh individual via SSE în loc de refresh total pagină
- Bonurile cu eroare OCR rămân vizibile pentru editare manuală
- Afișare nume fișier original pentru toate bonurile
- Upload stabil pe mobil (fix race condition File API)
- Păstrare ordine bonuri la refresh (nu se reordonează)

### Backend
- SSE endpoint pentru status updates real-time
- Bulk delete endpoint cu partial success
- Auto-cleanup bonuri failed după 7 zile
- Batch model cu tracking complet

### Testing
- E2E tests cu Playwright
- Unit tests pentru bulk upload, auto-create, cleanup

## Commits Squashed: 43 user stories (US-001 → US-043)
## Branch: ralph/bulk-receipt-upload
## Timp dezvoltare: ~3 zile (Ralph autonomous)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/modules/data_entry/db/models/receipt.py

@@ -36,6 +36,14 @@ class PaymentMode(str, Enum):
     AVANS_DECONTARE = "avans_decontare"  # Decont angajat (542)
 
 
+class ProcessingStatus(str, Enum):
+    """Processing status for bulk uploaded receipts."""
+    PENDING = "pending"          # Waiting in queue
+    PROCESSING = "processing"    # Currently being processed by OCR
+    COMPLETED = "completed"      # Successfully processed
+    FAILED = "failed"            # Processing failed with error
+
+
 if TYPE_CHECKING:
     from .accounting_entry import AccountingEntry
 
@@ -96,6 +104,14 @@ class Receipt(SQLModel, table=True):
     oracle_act_id: Optional[int] = Field(default=None)
     oracle_error: Optional[str] = Field(default=None, max_length=500)
 
+    # Bulk upload batch tracking
+    batch_id: Optional[str] = Field(default=None, max_length=50, index=True)
+    processing_status: Optional[str] = Field(default=None, max_length=20, index=True)  # ProcessingStatus enum value
+    processing_error: Optional[str] = Field(default=None)  # Full error message text
+    file_hash: Optional[str] = Field(default=None, max_length=64, index=True)  # SHA-256 hash for duplicate detection
+    processing_started_at: Optional[datetime] = Field(default=None)
+    processing_completed_at: Optional[datetime] = Field(default=None)
+
     # Relationships
     attachments: List["ReceiptAttachment"] = Relationship(
         back_populates="receipt",