feat(monitoring): add Redis exporter + Sentry docs to deployment guide

- Add redis-exporter container to docker-compose (oliver006/redis_exporter, 32MB)
- Add Redis scrape target to Prometheus config
- Add 4 Redis alert rules: RedisDown, HighMemory, HighConnections, RejectedConnections
- Document Step 19b (Sentry Error Tracking) in Hetzner deployment guide
- Document Step 19c (Redis Monitoring) in Hetzner deployment guide
- Update resource budget and port reference tables

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/architecture/theme-system/presets.md

@@ -100,28 +100,28 @@ def apply_theme_preset(
     db: Session = Depends(get_db),
 ):
     """Apply a theme preset to store."""
-    
+
     # Validate preset name
     if preset_name not in get_available_presets():
         raise HTTPException(
             status_code=400,
             detail=f"Invalid preset. Available: {get_available_presets()}"
         )
-    
+
     # Get or create store theme
     theme = db.query(StoreTheme).filter(
         StoreTheme.store_id == store.id
     ).first()
-    
+
     if not theme:
         theme = StoreTheme(store_id=store.id)
         db.add(theme)
-    
+
     # Apply preset
     apply_preset(theme, preset_name)
     db.commit()
     db.refresh(theme)
-    
+
     return {
         "message": f"Theme preset '{preset_name}' applied successfully",
         "theme": theme.to_dict()
@@ -135,12 +135,12 @@ def apply_theme_preset(
 def get_theme_presets():
     """Get all available theme presets with previews."""
     from app.core.theme_presets import get_available_presets, get_preset_preview
-    
+
     presets = []
     for preset_name in get_available_presets():
         preview = get_preset_preview(preset_name)
         presets.append(preview)
-    
+
     return {"presets": presets}
 
 # Returns:
@@ -302,16 +302,16 @@ from models.database.store_theme import StoreTheme
 def test_all_presets():
     """Test applying all presets"""
     presets = get_available_presets()
-    
+
     for preset_name in presets:
         theme = StoreTheme(store_id=999)  # Test store
         apply_preset(theme, preset_name)
-        
+
         assert theme.theme_name == preset_name
         assert theme.colors is not None
         assert theme.font_family_heading is not None
         assert theme.is_active == True
-        
+
         print(f"✅ {preset_name} preset OK")
 
 test_all_presets()