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/tools/database/queryDimensionNodes.ts

@@ -45,11 +45,11 @@ export const queryDimensionNodesTool = tool({
           dimensions: node.dimensions || [],
         };
 
-        if (includeContent && node.content) {
+        if (includeContent && node.notes) {
           // Truncate to ~100 chars
-          formatted.contentPreview = node.content.length > 100
-            ? node.content.substring(0, 100) + '...'
-            : node.content;
+          formatted.notesPreview = node.notes.length > 100
+            ? node.notes.substring(0, 100) + '...'
+            : node.notes;
         }
 
         return formatted;