feat: AI-generated shorts render pipeline

- Remotion composition (ShortsVideo) renders 1080x1920 9:16 shorts
  from script segments (hook/setup/conflict/insight/cta) with animated
  gradient background, word-by-word captions, progress bar
- render-worker.mjs: standalone poller (systemd hermyhq-render.service)
  TTS via edge-tts → Remotion render via Chrome headless → ffmpeg mux +
  thumbnail; ≤60s gate; marks YoutubeScript rendered
- API: POST /api/youtube/render (queue approved→render_queued),
  GET status, GET /render/file (stream video/thumb with Range support)
- Schema: YoutubeScript.videoUrl/thumbnailUrl + YoutubeRender model
- UI: youtube tab gains Renders view (preview/review/approve/reject/
  download), Render Shorts button on approved scripts
- Prisma db push applied to prod DB

remotion.config.ts

@@ -0,0 +1,2 @@
+import { Config } from "@remotion/cli/config";
+Config.setOverwriteOutput(true);