feat: add capacity planning docs, image upload system, and platform health monitoring

Documentation:
- Add comprehensive capacity planning guide (docs/architecture/capacity-planning.md)
- Add operations docs: platform-health, capacity-monitoring, image-storage
- Link pricing strategy to capacity planning documentation
- Update mkdocs.yml with new Operations section

Image Upload System:
- Add ImageService with WebP conversion and sharded directory structure
- Generate multiple size variants (original, 800px, 200px)
- Add storage stats endpoint for monitoring
- Add Pillow dependency for image processing

Platform Health Monitoring:
- Add /admin/platform-health page with real-time metrics
- Show CPU, memory, disk usage with progress bars
- Display capacity thresholds with status indicators
- Generate scaling recommendations automatically
- Determine infrastructure tier based on usage
- Add psutil dependency for system metrics

Admin UI:
- Add Capacity Monitor to Platform Health section in sidebar
- Create platform-health.html template with stats cards
- Create platform-health.js for Alpine.js state management

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

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

models/schema/image.py

@@ -0,0 +1,46 @@
+# models/schema/image.py
+"""
+Pydantic schemas for image operations.
+"""
+
+from pydantic import BaseModel
+
+
+class ImageUrls(BaseModel):
+    """URLs for image variants."""
+
+    original: str
+    medium: str | None = None  # 800px variant
+    thumb: str | None = None  # 200px variant
+
+    # Allow arbitrary keys for flexibility
+    class Config:
+        extra = "allow"
+
+
+class ImageUploadResponse(BaseModel):
+    """Response from image upload."""
+
+    success: bool
+    image: dict | None = None
+    error: str | None = None
+
+
+class ImageDeleteResponse(BaseModel):
+    """Response from image deletion."""
+
+    success: bool
+    message: str
+
+
+class ImageStorageStats(BaseModel):
+    """Image storage statistics."""
+
+    total_files: int
+    total_size_bytes: int
+    total_size_mb: float
+    total_size_gb: float
+    directory_count: int
+    max_files_per_dir: int
+    avg_files_per_dir: float
+    products_estimated: int