feat: final schema pass — sync 9 schema changes from main repo

- Rename nodes.content → nodes.notes across all services, tools, API routes, and UI
- Add dimensions.icon column support (GET/POST routes, types)
- Add nodes.event_date column (create/update flows, types)
- Drop nodes.type and nodes.is_pinned references
- Drop edges.user_feedback references
- Drop chat_memory_state table (replaced with DROP IF EXISTS in migration)
- Update schema guide files (system/schema.md)
- Add runtime migration block in sqlite-client.ts for existing databases
- Fix MCP tool schemas (external API keeps 'content' param, maps to 'notes' internally)
- Update standalone MCP server (nodeService.js, sqlite-client.js, index.js)
- Update HTTP MCP server (server.js, stdio-server.js)
- Update all extraction tools (paper, website, youtube)
- Update all UI components (FocusPanel, ThreePanelLayout, GridView, ListView, FolderViewOverlay)
- TypeScript: 0 errors

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/types/database.ts

@@ -3,16 +3,16 @@ export interface Node {
   id: number;
   title: string;
   description?: string;
-  content?: string;           // Consolidated content from description + abstract + notes
+  notes?: string;           // Consolidated content from description + abstract + notes
   link?: string;
-  type?: string;
+  event_date?: string;
   dimensions: string[];       // Flexible dimensions replacing type + stage + segment + tags
   embedding?: Buffer;         // Node-level embedding (BLOB data)
   chunk?: string;
   metadata?: any;            // Flexible metadata storage from extras + chunk_status + sub_type
   created_at: string;
   updated_at: string;
-  is_pinned?: number;        // Legacy pin flag (read-only, slated for removal)
+        // Legacy pin flag (read-only, slated for removal)
   edge_count?: number;       // Derived count of edges, included in some queries
 
   // Optional embedding fields (restored from migration)