feat(render+templates): Remotion engine, 16 branded templates (incl. 3D), seconds pricing, coming-soon

Render engine
- Add Remotion (code-based) as a 2nd render engine alongside After Effects.
  node-agent dispatches on Job.Engine; RunRemotion maps bindings -> --props,
  renders native then ffmpeg-scales to the quality tier (aspect-preserving).
- content.projects.render_engine + render_remotion_comp (migration 32);
  render-svc claim resolves engine and routes (skips .aep for Remotion).
- Admin TemplatesAdmin gains an engine picker + Remotion composition id field.

Template pack (services/remotion)
- 16 branded, Persian (Vazirmatn), color- and text-editable templates, each in
  3 aspects (16:9 / 1:1 / 9:16): LogoMotion, Opener, InstaPromo, YouTubeIntro,
  Slideshow, HappyBirthday, SalePromo, QuoteCard, EventInvite, Countdown,
  GlitterReveal (editable logo image), NowruzGreeting (animated characters),
  and 4 cinematic 3D templates via @remotion/three (Hero3D, Nowruz3D,
  Birthday3D, Promo3D) with reflections + bloom/DOF/vignette.
- scripts/seed_remotion_templates.py seeds containers/projects/scenes/colors.

Pricing
- Rewrite /pricing to the seconds-based model (charge = length x resolution),
  data-driven from /v1/plans, Toman, broker checkout.

Coming-soon
- Persian experimental-build overlay on all pages (launch date + countdown).

Fixes
- middleware matcher bypasses all static asset paths; catalog mapping passes
  cover image + preview video so real thumbnails render.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/db/migrations/32_content_render_engine.sql

@@ -0,0 +1,16 @@
+-- 32_content_render_engine.sql
+-- Two render engines per template: After Effects (.aep, rendered by a node-agent)
+-- and Remotion (code-based React composition). render_engine selects which; for
+-- Remotion templates render_remotion_comp holds the composition id to render
+-- (the .aep / render_aep_comp columns stay null for those).
+--
+-- Apply manually on the live DB (migrations are not auto-run):
+--   docker exec -i <postgres> psql -U postgres -d flatrender < 32_content_render_engine.sql
+
+ALTER TABLE content.projects
+    ADD COLUMN IF NOT EXISTS render_engine TEXT NOT NULL DEFAULT 'AfterEffects';
+
+ALTER TABLE content.projects
+    ADD COLUMN IF NOT EXISTS render_remotion_comp TEXT;
+
+-- Existing templates are all After Effects; the default already covers them.