feat: per-site QR menu mode (order vs view-only) + editable branding

Adds a sysadmin-configurable toggle so sites can disable online ordering
on the public QR menu until it's fully supported, plus editable
tagline/hours and a header image (replacing the hardcoded "Our Menu"
placeholder) — all previously hardcoded frontend strings.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

cloud_backend/schemas/site.py

@@ -15,6 +15,11 @@ class SiteUpdate(BaseModel):
     contact_email: str | None = None
     license_expires_at: datetime | None = None
     waiter_domain: str | None = None
+    menu_mode: str | None = None
+    menu_tagline_en: str | None = None
+    menu_tagline_gr: str | None = None
+    menu_hours_en: str | None = None
+    menu_hours_gr: str | None = None
 
 
 class SiteOut(BaseModel):
@@ -32,6 +37,12 @@ class SiteOut(BaseModel):
     last_seen_ip: str | None
     last_seen_local_ip: str | None
     waiter_domain: str | None
+    menu_mode: str
+    menu_tagline_en: str | None
+    menu_tagline_gr: str | None
+    menu_hours_en: str | None
+    menu_hours_gr: str | None
+    menu_header_image_url: str | None
 
     model_config = {"from_attributes": True}