feat(api): .NET 10 multi-tenant REST API

Full backend implementation:
- Multi-tenant cafe/restaurant management (menus, orders, tables, staff)
- POS order flow with ZarinPal and Snappfood payment integration
- OTP authentication via Kavenegar SMS
- QR digital menu with public discover/finder endpoints
- Customer loyalty, coupons, CRM
- PostgreSQL via EF Core, Redis for caching/sessions
- Background jobs, webhook handlers
- Full migration history

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

data/cafe-theme-presets.json

@@ -0,0 +1,14 @@
+{
+  "version": 1,
+  "palettes": [
+    "meezi-green", "ocean-blue", "royal-purple", "sunset-orange", "rose-blush",
+    "charcoal-gold", "espresso", "forest", "midnight", "coral", "gold-luxury",
+    "mint-fresh", "wine-bar", "slate-modern", "cherry", "teal-wave", "sand-cafe"
+  ],
+  "panelStyles": ["flat", "modern", "glass", "minimal", "bold", "soft", "elevated", "outline"],
+  "menuStyles": ["cards", "compact", "grid", "list", "magazine", "classic"],
+  "menuTextures": ["none", "paper", "linen", "dots", "grid", "marble", "wood", "warm"],
+  "densities": ["compact", "comfortable", "spacious"],
+  "radius": ["none", "sm", "md", "lg", "full"],
+  "customColorKeys": ["primary", "secondary", "accent", "background", "surface", "text", "textMuted", "destructive", "success"]
+}