Ship Print Forge shop site (colors, photos, 3D viewer) (#2)

## Summary

- Rebrand the Django client template as Print Forge (`client_site` → `print_forge`) with shop + shipping enabled.
- Product listings support multiple photos, color variants (shared price/description/STL, per-color stock and photos), and a photo-first / 3D-second gallery.
- Public pages use 3D printer / printed-toy photography instead of leftover t-shirt mockups; beta CI deploys on `master`.

Closes #1
Infra: [server-infra#27](ai_ml_operations/server-infra#27) (easy deploy beta).

## Test plan

- [ ] Product page shows photo first, 3D model second; color swatches swap photos and stock
- [ ] Portal can upload multiple photos and per-color qty/images; STL stays shared
- [ ] Public home/about/gallery have no t-shirt mockups
- [ ] `manage.py test` passes
- [ ] After server-infra#27: beta deploy to `print-forge-preview.aimloperations.com`

Reviewed-on: #2

site/public/context_processors.py

@@ -34,6 +34,20 @@ def site_branding(request):
     }
 
 
+def shop_cart(request):
+    from django.apps import apps as django_apps
+
+    if not django_apps.is_installed("shop"):
+        return {"cart_count": 0}
+    session = getattr(request, "session", None)
+    if session is None:
+        return {"cart_count": 0}
+    from shop.services import cart_lines
+
+    lines = cart_lines(session)
+    return {"cart_count": sum(line["quantity"] for line in lines)}
+
+
 def tianji_tracking(request):
     match = getattr(request, "resolver_match", None)
     url_name = getattr(match, "url_name", "") or ""
@@ -63,6 +77,15 @@ def tianji_tracking(request):
         nav_section = "social_accounts"
     elif namespace == "social":
         nav_section = "social"
+    elif namespace == "shop_portal":
+        if url_name.startswith("product"):
+            nav_section = "shop_products"
+        elif url_name.startswith("order"):
+            nav_section = "shop_orders"
+        elif url_name == "sales":
+            nav_section = "shop_sales"
+    elif namespace == "shop":
+        nav_section = "shop"
 
     return {
         "tianji_enabled": getattr(settings, "TIANJI_ENABLED", False)