feat: implement section-based homepage management system

Add structured JSON sections to ContentPage for multi-language homepage editing:

Database:
- Add `sections` JSON column to content_pages table
- Migration z8i9j0k1l2m3 adds the column

Schema:
- New models/schema/homepage_sections.py with Pydantic schemas
- TranslatableText for language-keyed translations
- HeroSection, FeaturesSection, PricingSection, CTASection

Templates:
- New section partials in app/templates/platform/sections/
- Updated homepage-default.html to render sections dynamically
- Fallback to placeholder content when sections not configured

Service:
- update_homepage_sections() - validate and save all sections
- update_single_section() - update individual section
- get_default_sections() - empty structure for new homepages

API:
- GET /{page_id}/sections - get sections with platform languages
- PUT /{page_id}/sections - update all sections
- PUT /{page_id}/sections/{section_name} - update single section

Admin UI:
- Section editor appears when editing homepage (slug='home')
- Language tabs from platform.supported_languages
- Accordion sections for Hero, Features, Pricing, CTA
- Button/feature card repeaters with add/remove

Also fixes broken line 181 in z4e5f6a7b8c9 migration.

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

app/api/v1/admin/content_pages.py

@@ -284,3 +284,116 @@ def delete_page(
     """Delete a content page."""
     content_page_service.delete_page_or_raise(db, page_id)
     db.commit()
+
+
+# ============================================================================
+# HOMEPAGE SECTIONS MANAGEMENT
+# ============================================================================
+
+
+class HomepageSectionsResponse(BaseModel):
+    """Response containing homepage sections with platform language info."""
+
+    sections: dict | None = None
+    supported_languages: list[str] = Field(default_factory=lambda: ["fr", "de", "en"])
+    default_language: str = "fr"
+
+
+class SectionUpdateResponse(BaseModel):
+    """Response after updating sections."""
+
+    message: str
+    sections: dict | None = None
+
+
+@router.get("/{page_id}/sections", response_model=HomepageSectionsResponse)
+def get_page_sections(
+    page_id: int,
+    current_user: User = Depends(get_current_admin_api),
+    db: Session = Depends(get_db),
+):
+    """
+    Get homepage sections for a content page.
+
+    Returns sections along with platform language settings for the editor.
+    """
+    page = content_page_service.get_page_by_id_or_raise(db, page_id)
+
+    # Get platform languages
+    platform = page.platform
+    supported_languages = (
+        platform.supported_languages if platform else ["fr", "de", "en"]
+    )
+    default_language = platform.default_language if platform else "fr"
+
+    return {
+        "sections": page.sections,
+        "supported_languages": supported_languages,
+        "default_language": default_language,
+    }
+
+
+@router.put("/{page_id}/sections", response_model=SectionUpdateResponse)
+def update_page_sections(
+    page_id: int,
+    sections: dict,
+    current_user: User = Depends(get_current_admin_api),
+    db: Session = Depends(get_db),
+):
+    """
+    Update all homepage sections at once.
+
+    Expected structure:
+    {
+        "hero": { ... },
+        "features": { ... },
+        "pricing": { ... },
+        "cta": { ... }
+    }
+    """
+    page = content_page_service.update_homepage_sections(
+        db,
+        page_id=page_id,
+        sections=sections,
+        updated_by=current_user.id,
+    )
+    db.commit()
+
+    return {
+        "message": "Sections updated successfully",
+        "sections": page.sections,
+    }
+
+
+@router.put("/{page_id}/sections/{section_name}", response_model=SectionUpdateResponse)
+def update_single_section(
+    page_id: int,
+    section_name: str,
+    section_data: dict,
+    current_user: User = Depends(get_current_admin_api),
+    db: Session = Depends(get_db),
+):
+    """
+    Update a single section (hero, features, pricing, or cta).
+
+    section_name must be one of: hero, features, pricing, cta
+    """
+    if section_name not in ["hero", "features", "pricing", "cta"]:
+        raise ValidationException(
+            message=f"Invalid section name: {section_name}. Must be one of: hero, features, pricing, cta",
+            field="section_name",
+        )
+
+    page = content_page_service.update_single_section(
+        db,
+        page_id=page_id,
+        section_name=section_name,
+        section_data=section_data,
+        updated_by=current_user.id,
+    )
+    db.commit()
+
+    return {
+        "message": f"Section '{section_name}' updated successfully",
+        "sections": page.sections,
+    }