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>

alembic/versions/z4e5f6a7b8c9_add_multi_platform_support.py

@@ -178,7 +178,9 @@ def upgrade() -> None:
         """)
     )
 
-I dn
+    # Get OMS platform ID for backfilling
+    result = conn.execute(sa.text("SELECT id FROM platforms WHERE code = 'oms'"))
+    oms_platform_id = result.fetchone()[0]
 
     # =========================================================================
     # 6. Backfill content_pages with platform_id

alembic/versions/z8i9j0k1l2m3_add_sections_to_content_pages.py

@@ -0,0 +1,36 @@
+"""Add sections column to content_pages
+
+Revision ID: z8i9j0k1l2m3
+Revises: z7h8i9j0k1l2
+Create Date: 2026-01-23
+
+Adds sections JSON column for structured homepage editing with multi-language support.
+The sections column stores hero, features, pricing, and cta configurations
+with TranslatableText pattern for i18n.
+"""
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = "z8i9j0k1l2m3"
+down_revision = "z7h8i9j0k1l2"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "content_pages",
+        sa.Column(
+            "sections",
+            sa.JSON(),
+            nullable=True,
+            comment="Structured homepage sections (hero, features, pricing, cta) with i18n",
+        ),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("content_pages", "sections")