feat(i18n): complete post-launch i18n phases 5-8

- Phase 5: Translate homepage-modern.html (~90 new locale keys, all
  hardcoded strings replaced with _() calls for dashboard mock,
  features, pricing tiers, testimonial sections)
- Phase 6: Translate homepage-minimal.html (17 new locale keys for
  fallback content, features, and CTA sections)
- Phase 7: Add multi-language page.title/content support with
  title_translations and content_translations JSON columns, Alembic
  migration cms_002, translated title/content resolution in templates,
  and seed script updates with tt() helper
- Phase 8: Complete lb.json audit — fill 6 missing keys (messages,
  confirmations), also backfill same keys in fr.json and de.json

All 4 locale files now have 340 keys with full parity.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/modules/cms/schemas/homepage_sections.py

@@ -85,6 +85,7 @@ class ProductCard(BaseModel):
     description: TranslatableText = Field(default_factory=TranslatableText)
     url: str = ""
     badge: TranslatableText | None = None
+    link_text: TranslatableText | None = None
 
 
 class ProductsSection(BaseModel):
@@ -115,6 +116,15 @@ class PricingSection(BaseModel):
     use_subscription_tiers: bool = Field(
         default=True, description="Pull pricing from subscription_tiers table dynamically"
     )
+    # UI label overrides (CMS-driven, with hardcoded English fallback in template)
+    monthly_label: TranslatableText | None = None
+    annual_label: TranslatableText | None = None
+    save_text: TranslatableText | None = None
+    popular_badge: TranslatableText | None = None
+    cta_text: TranslatableText | None = None
+    per_month_label: TranslatableText | None = None
+    per_year_label: TranslatableText | None = None
+    coming_soon_text: TranslatableText | None = None
 
 
 class CTASection(BaseModel):