feat(studio): full Blocks panel — browse, search, add, drag-and-drop registry items

Adds a Blocks tab to the Studio left sidebar with the full 78-item registry
catalog (58 blocks + 20 components). Users can browse by category, search by
title/description, preview CDN-hosted poster thumbnails with video-on-hover,
and install items on-demand with one click or drag-to-timeline.

Core changes:
- BlockCategory type + resolveBlockCategory() for 7 categories (Captions, VFX,
  Transitions, Effects, Social, Data, Scenes)
- Registry API routes: GET /api/registry/blocks (catalog) + POST install
- StudioApiAdapter extended with listRegistryCatalog + installRegistryBlock
- Vite adapter reads from disk; CLI adapter fetches from GitHub (24h cache)
- BlockParam interface + params on 6 blocks for future parameter controls

Studio UI:
- 4th sidebar tab "Blocks" with responsive grid, category pills, search bar
- BlockCard: CDN poster thumbnail, video autoplay on hover, duration + WebGL badges
- On-demand install: blocks append as sub-compositions on timeline; components
  overlay at start=0 spanning full duration with transparent background patching
- TIMELINE_BLOCK_MIME drag-and-drop to timeline
- BlockParamsPanel (Phase 3 scaffold) auto-opens for parameterized blocks

Registry manifests:
- All 58 blocks backfilled with preview: { video, poster } CDN URLs
- All 20 components normalized to object format + poster URLs added
- 6 blocks annotated with params (Liquid Glass/Background, Portal, Chart,
  Logo Outro, Magnetic)
- flowchart-vertical preview generated and uploaded to CDN

registry/blocks/transitions-push/registry-item.json

@@ -16,5 +16,9 @@
       "target": "compositions/transitions-push.html",
       "type": "hyperframes:composition"
     }
-  ]
+  ],
+  "preview": {
+    "video": "https://static.heygen.ai/hyperframes-oss/docs/images/catalog/blocks/transitions-push.mp4",
+    "poster": "https://static.heygen.ai/hyperframes-oss/docs/images/catalog/blocks/transitions-push.png"
+  }
 }