refactor: modernize code quality tooling with Ruff

- Replace black, isort, and flake8 with Ruff (all-in-one linter and formatter)
- Add comprehensive pyproject.toml configuration
- Simplify Makefile code quality targets
- Configure exclusions for venv/.venv in pyproject.toml
- Auto-fix 1,359 linting issues across codebase

Benefits:
- Much faster builds (Ruff is written in Rust)
- Single tool replaces multiple tools
- More comprehensive rule set (UP, B, C4, SIM, PIE, RET, Q)
- All configuration centralized in pyproject.toml
- Better import sorting and formatting consistency

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

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

models/schema/marketplace_import_job.py

@@ -1,5 +1,4 @@
 from datetime import datetime
-from typing import Optional
 
 from pydantic import BaseModel, ConfigDict, Field, field_validator
 
@@ -12,7 +11,7 @@ class MarketplaceImportJobRequest(BaseModel):
 
     source_url: str = Field(..., description="URL to CSV file from marketplace")
     marketplace: str = Field(default="Letzshop", description="Marketplace name")
-    batch_size: Optional[int] = Field(
+    batch_size: int | None = Field(
         1000, description="Processing batch size", ge=100, le=10000
     )
 
@@ -50,12 +49,12 @@ class MarketplaceImportJobResponse(BaseModel):
     error_count: int = 0
 
     # Error details
-    error_message: Optional[str] = None
+    error_message: str | None = None
 
     # Timestamps
     created_at: datetime
-    started_at: Optional[datetime] = None
-    completed_at: Optional[datetime] = None
+    started_at: datetime | None = None
+    completed_at: datetime | None = None
 
 
 class MarketplaceImportJobListResponse(BaseModel):
@@ -71,8 +70,8 @@ class MarketplaceImportJobStatusUpdate(BaseModel):
     """Schema for updating import job status (internal use)."""
 
     status: str
-    imported_count: Optional[int] = None
-    updated_count: Optional[int] = None
-    error_count: Optional[int] = None
-    total_processed: Optional[int] = None
-    error_message: Optional[str] = None
+    imported_count: int | None = None
+    updated_count: int | None = None
+    error_count: int | None = None
+    total_processed: int | None = None
+    error_message: str | None = None