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

packages/studio/src/utils/studioUiPreferences.ts

@@ -10,6 +10,7 @@ export interface StudioUiPreferences {
   playbackRate?: number;
   audioMuted?: boolean;
   previewZoom?: StoredPreviewZoomState;
+  recentBlocks?: string[];
 }
 
 const STUDIO_UI_PREFERENCES_KEY = "hf-studio-ui-preferences";
@@ -61,6 +62,11 @@ function readStorage(storage: Storage | null): StudioUiPreferences {
         preferences.previewZoom = { zoomPercent, panX, panY };
       }
     }
+    if (Array.isArray(parsed.recentBlocks)) {
+      preferences.recentBlocks = parsed.recentBlocks.filter(
+        (v: unknown): v is string => typeof v === "string",
+      );
+    }
     return preferences;
   } catch {
     return {};