feat: add CMS service layer and API endpoints

Implement complete CMS business logic and REST API:

Service Layer (content_page_service.py):
- get_page_for_vendor() - Two-tier lookup with fallback
- list_pages_for_vendor() - Merge vendor + platform pages
- create_page(), update_page(), delete_page() - CRUD operations
- Support for published/draft workflow
- Footer/header navigation filtering

API Endpoints:

Admin API (/api/v1/admin/content-pages):
- POST /platform - Create platform defaults
- GET /platform - List platform defaults
- GET / - List all pages with vendor filtering
- PUT /{id} - Update any page
- DELETE /{id} - Delete any page

Vendor API (/api/v1/vendor/{code}/content-pages):
- GET / - List available pages (vendor + platform merged)
- GET /overrides - List only vendor overrides
- POST / - Create vendor override
- PUT /{id} - Update vendor page
- DELETE /{id} - Delete vendor page

Shop API (/api/v1/shop/content-pages):
- GET /navigation - Get footer/header navigation pages
- GET /{slug} - Get specific page (public, with fallback)

All endpoints include proper authentication, authorization,
and validation using Pydantic schemas.

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

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

app/api/v1/shop/__init__.py

@@ -0,0 +1,25 @@
+# app/api/v1/shop/__init__.py
+"""
+Shop API router aggregation.
+
+This module aggregates all shop-related JSON API endpoints (public facing).
+
+These are PUBLIC endpoints - no authentication required.
+"""
+
+from fastapi import APIRouter
+
+# Import shop routers
+from . import content_pages
+
+# Create shop router
+router = APIRouter()
+
+# ============================================================================
+# PUBLIC API ROUTES
+# ============================================================================
+
+# Content pages (about, faq, contact, etc.)
+router.include_router(content_pages.router, prefix="/content-pages", tags=["shop-content-pages"])
+
+__all__ = ["router"]

app/api/v1/shop/content_pages.py

@@ -0,0 +1,116 @@
+# app/api/v1/shop/content_pages.py
+"""
+Shop Content Pages API (Public)
+
+Public endpoints for retrieving content pages in shop frontend.
+No authentication required.
+"""
+
+import logging
+from typing import List
+from fastapi import APIRouter, Depends, HTTPException, Request
+from pydantic import BaseModel
+from sqlalchemy.orm import Session
+
+from app.core.database import get_db
+from app.services.content_page_service import content_page_service
+
+router = APIRouter()
+logger = logging.getLogger(__name__)
+
+
+# ============================================================================
+# RESPONSE SCHEMAS
+# ============================================================================
+
+class PublicContentPageResponse(BaseModel):
+    """Public content page response (no internal IDs)."""
+    slug: str
+    title: str
+    content: str
+    content_format: str
+    meta_description: str | None
+    meta_keywords: str | None
+    published_at: str | None
+
+
+class ContentPageListItem(BaseModel):
+    """Content page list item for navigation."""
+    slug: str
+    title: str
+    show_in_footer: bool
+    show_in_header: bool
+    display_order: int
+
+
+# ============================================================================
+# PUBLIC ENDPOINTS
+# ============================================================================
+
+@router.get("/navigation", response_model=List[ContentPageListItem])
+def get_navigation_pages(
+    request: Request,
+    db: Session = Depends(get_db)
+):
+    """
+    Get list of content pages for navigation (footer/header).
+
+    Uses vendor from request.state (set by middleware).
+    Returns vendor overrides + platform defaults.
+    """
+    vendor = getattr(request.state, 'vendor', None)
+    vendor_id = vendor.id if vendor else None
+
+    # Get all published pages for this vendor
+    pages = content_page_service.list_pages_for_vendor(
+        db,
+        vendor_id=vendor_id,
+        include_unpublished=False
+    )
+
+    return [
+        {
+            "slug": page.slug,
+            "title": page.title,
+            "show_in_footer": page.show_in_footer,
+            "show_in_header": page.show_in_header,
+            "display_order": page.display_order,
+        }
+        for page in pages
+    ]
+
+
+@router.get("/{slug}", response_model=PublicContentPageResponse)
+def get_content_page(
+    slug: str,
+    request: Request,
+    db: Session = Depends(get_db)
+):
+    """
+    Get a specific content page by slug.
+
+    Uses vendor from request.state (set by middleware).
+    Returns vendor override if exists, otherwise platform default.
+    """
+    vendor = getattr(request.state, 'vendor', None)
+    vendor_id = vendor.id if vendor else None
+
+    page = content_page_service.get_page_for_vendor(
+        db,
+        slug=slug,
+        vendor_id=vendor_id,
+        include_unpublished=False  # Only show published pages
+    )
+
+    if not page:
+        raise HTTPException(status_code=404, detail=f"Content page not found: {slug}")
+
+    return {
+        "slug": page.slug,
+        "title": page.title,
+        "content": page.content,
+        "content_format": page.content_format,
+        "meta_description": page.meta_description,
+        "meta_keywords": page.meta_keywords,
+        "published_at": page.published_at.isoformat() if page.published_at else None,
+    }