feat: add vendor API endpoints for inventory transaction history

Adds three new endpoints for viewing stock movement history:
- GET /inventory/transactions - paginated list with filters
- GET /inventory/transactions/product/{id} - product-specific history
- GET /inventory/transactions/order/{id} - order-specific history

Creates InventoryTransactionService to encapsulate query logic
following architecture patterns. Includes response schemas with
product details for rich UI display.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/api/v1/vendor/inventory.py

@@ -14,6 +14,7 @@ from sqlalchemy.orm import Session
 from app.api.deps import get_current_vendor_api
 from app.core.database import get_db
 from app.services.inventory_service import inventory_service
+from app.services.inventory_transaction_service import inventory_transaction_service
 from models.database.user import User
 from models.schema.inventory import (
     InventoryAdjust,
@@ -22,8 +23,12 @@ from models.schema.inventory import (
     InventoryMessageResponse,
     InventoryReserve,
     InventoryResponse,
+    InventoryTransactionListResponse,
+    InventoryTransactionWithProduct,
     InventoryUpdate,
+    OrderTransactionHistoryResponse,
     ProductInventorySummary,
+    ProductTransactionHistoryResponse,
 )
 
 router = APIRouter()
@@ -159,3 +164,94 @@ def delete_inventory(
     inventory_service.delete_inventory(db, current_user.token_vendor_id, inventory_id)
     db.commit()
     return InventoryMessageResponse(message="Inventory deleted successfully")
+
+
+# ============================================================================
+# Inventory Transaction History Endpoints
+# ============================================================================
+
+
+@router.get("/inventory/transactions", response_model=InventoryTransactionListResponse)
+def get_inventory_transactions(
+    skip: int = Query(0, ge=0),
+    limit: int = Query(50, ge=1, le=200),
+    product_id: int | None = Query(None, description="Filter by product"),
+    transaction_type: str | None = Query(None, description="Filter by type"),
+    current_user: User = Depends(get_current_vendor_api),
+    db: Session = Depends(get_db),
+):
+    """
+    Get inventory transaction history for the vendor.
+
+    Returns a paginated list of all stock movements with product details.
+    Use filters to narrow down by product or transaction type.
+    """
+    transactions, total = inventory_transaction_service.get_vendor_transactions(
+        db=db,
+        vendor_id=current_user.token_vendor_id,
+        skip=skip,
+        limit=limit,
+        product_id=product_id,
+        transaction_type=transaction_type,
+    )
+
+    return InventoryTransactionListResponse(
+        transactions=[InventoryTransactionWithProduct(**tx) for tx in transactions],
+        total=total,
+        skip=skip,
+        limit=limit,
+    )
+
+
+@router.get(
+    "/inventory/transactions/product/{product_id}",
+    response_model=ProductTransactionHistoryResponse,
+)
+def get_product_transaction_history(
+    product_id: int,
+    limit: int = Query(50, ge=1, le=200),
+    current_user: User = Depends(get_current_vendor_api),
+    db: Session = Depends(get_db),
+):
+    """
+    Get transaction history for a specific product.
+
+    Returns recent stock movements with current inventory status.
+    """
+    result = inventory_transaction_service.get_product_history(
+        db=db,
+        vendor_id=current_user.token_vendor_id,
+        product_id=product_id,
+        limit=limit,
+    )
+
+    return ProductTransactionHistoryResponse(**result)
+
+
+@router.get(
+    "/inventory/transactions/order/{order_id}",
+    response_model=OrderTransactionHistoryResponse,
+)
+def get_order_transaction_history(
+    order_id: int,
+    current_user: User = Depends(get_current_vendor_api),
+    db: Session = Depends(get_db),
+):
+    """
+    Get all inventory transactions for a specific order.
+
+    Shows all stock movements (reserve, fulfill, release) related to an order.
+    """
+    result = inventory_transaction_service.get_order_history(
+        db=db,
+        vendor_id=current_user.token_vendor_id,
+        order_id=order_id,
+    )
+
+    return OrderTransactionHistoryResponse(
+        order_id=result["order_id"],
+        order_number=result["order_number"],
+        transactions=[
+            InventoryTransactionWithProduct(**tx) for tx in result["transactions"]
+        ],
+    )