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/services/database/edges.ts

@@ -430,9 +430,9 @@ export class EdgeService {
           ELSE n_from.title
         END as connected_node_title,
         CASE 
-          WHEN e.from_node_id = ? THEN n_to.content
-          ELSE n_from.content
-        END as connected_node_content,
+          WHEN e.from_node_id = ? THEN n_to.notes
+          ELSE n_from.notes
+        END as connected_node_notes,
         CASE 
           WHEN e.from_node_id = ? THEN n_to.link
           ELSE n_from.link
@@ -499,7 +499,7 @@ export class EdgeService {
       const connected_node: Node = {
         id: row.connected_node_id,
         title: row.connected_node_title,
-        content: row.connected_node_content,
+        notes: row.connected_node_notes,
         link: row.connected_node_link,
         dimensions: row.connected_node_dimensions,
         embedding: undefined, // Not needed for display
@@ -544,7 +544,7 @@ export class EdgeService {
       const connected_node: Node = {
         id: row.connected_node_id,
         title: row.connected_node_title,
-        content: row.connected_node_content,
+        notes: row.connected_node_notes,
         link: row.connected_node_link,
         dimensions: JSON.parse(row.connected_node_dimensions_json || '[]'),
         embedding: undefined, // Not needed for display