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/migrations/versions/cms_002_add_title_content_translations.py

@@ -0,0 +1,41 @@
+"""add title_translations and content_translations to content_pages
+
+Revision ID: cms_002
+Revises: cms_001
+Create Date: 2026-03-02
+"""
+
+import sqlalchemy as sa
+
+from alembic import op
+
+revision = "cms_002"
+down_revision = "cms_001"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "content_pages",
+        sa.Column(
+            "title_translations",
+            sa.JSON(),
+            nullable=True,
+            comment="Language-keyed title dict for multi-language support",
+        ),
+    )
+    op.add_column(
+        "content_pages",
+        sa.Column(
+            "content_translations",
+            sa.JSON(),
+            nullable=True,
+            comment="Language-keyed content dict for multi-language support",
+        ),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("content_pages", "content_translations")
+    op.drop_column("content_pages", "title_translations")