Upgrade Remotion composition engine with cinematic enhancements

- Upgrade Remotion packages to 4.0.441, add transitions/captions/fonts/media
- Add spring-animated image scenes, stat reveals, section titles, hero cards
- Add TikTok-style word-by-word captions with highlight effect
- Add Google Fonts (Space Grotesk) and dynamic duration via calculateMetadata
- Fix Remotion false-positive: check node_modules/ in _remotion_available()
- Add project directory convention, music library, tool naming docs
- Add music transparency to proposal stage, subtitle pipeline to compose stage
- Add README showcase montage and Windows npm troubleshooting note

.gitignore

@@ -21,6 +21,12 @@ output/
 pipeline/
 tests/qa/output/
 
+# Project workspaces (generated assets, renders — all regenerable)
+projects/
+
+# User music library (personal royalty-free tracks — not part of repo)
+music_library/
+
 # Environment
 .env
 .env.local
@@ -42,3 +48,7 @@ Thumbs.db
 
 # Node (for remotion-composer/)
 node_modules/
+
+# Remotion build output and copied project assets (regenerable at render time)
+remotion-composer/out/
+remotion-composer/public/