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/batch.py

@@ -0,0 +1,64 @@
+"""BatchUpload and BatchJob SQLModel models for bulk receipt processing."""
+
+from datetime import datetime
+from enum import Enum
+from typing import Optional
+
+from sqlmodel import SQLModel, Field
+
+
+class BatchStatus(str, Enum):
+    """Status of a batch upload."""
+    PENDING = "pending"          # Batch created, jobs queued
+    PROCESSING = "processing"    # At least one job is processing
+    COMPLETED = "completed"      # All jobs completed (success or failed)
+    FAILED = "failed"            # Batch-level failure (e.g., all jobs failed)
+
+
+class BatchUpload(SQLModel, table=True):
+    """
+    Batch upload record for grouping multiple OCR jobs.
+
+    Tracks overall progress and status of a bulk upload operation.
+    """
+
+    __tablename__ = "batch_uploads"
+
+    id: Optional[int] = Field(default=None, primary_key=True)
+
+    # User info
+    user_id: str = Field(max_length=100, index=True)  # Username who created the batch
+    company_id: int = Field(index=True)  # Company ID for receipt creation
+
+    # Timestamps
+    created_at: datetime = Field(default_factory=datetime.utcnow)
+
+    # Status tracking
+    status: BatchStatus = Field(default=BatchStatus.PENDING)
+    total_files: int = Field(default=0)
+
+
+class BatchJob(SQLModel, table=True):
+    """
+    Junction table linking batch_uploads to ocr_jobs.
+
+    Each record represents one file in a batch, linking to its OCR job.
+    Also stores the receipt_id once the job completes and auto-creates a receipt.
+    """
+
+    __tablename__ = "batch_jobs"
+
+    id: Optional[int] = Field(default=None, primary_key=True)
+
+    # Foreign keys
+    batch_id: int = Field(foreign_key="batch_uploads.id", index=True)
+    job_id: str = Field(max_length=36, index=True)  # UUID from ocr_jobs table
+
+    # Original filename for display
+    filename: str = Field(max_length=255)
+
+    # Receipt reference (set after auto-create)
+    receipt_id: Optional[int] = Field(default=None, foreign_key="receipts.id")
+
+    # Timestamps
+    created_at: datetime = Field(default_factory=datetime.utcnow)