fix: Link creation broken due to ID vs URI mismatch

Fixed bug where links between nodes weren't being created.

Root Cause:
- UI sends node IDs in links array (e.g., "node:xxxxx")
- API query expected ATProto URIs (e.g., "at://did:plc:.../app.bsky.feed.post/...")
- Query: WHERE atp_uri IN $links never matched
- Result: Zero links created in database

Fix:
- Changed query to: WHERE id IN $links
- Now correctly matches node IDs from UI
- Added logging to track link creation
- Updated comments to clarify expected format

Impact:
Links selected in the edit UI will now be properly created and
visible as connections in the 3D thought galaxy visualization.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/api/nodes/route.ts

@@ -257,14 +257,17 @@ export async function POST(request: NextRequest) {
 
     // Handle linking
     if (links && links.length > 0) {
-      // Find the corresponding cache nodes for the AT-URIs
+      // Links array contains node IDs (e.g., "node:xxxxx") from the UI
+      // Verify they belong to this user before creating relations
       const targetNodesResult = await db.query<[Array<{ id: string }>]>(
-        'SELECT id FROM node WHERE user_did = $did AND atp_uri IN $links',
+        'SELECT id FROM node WHERE user_did = $did AND id IN $links',
         { did: userDid, links: links }
       );
 
       const targetNodes = targetNodesResult[0] || [];
 
+      console.log(`[POST /api/nodes] Creating ${targetNodes.length} link relations`);
+
       // Create graph relations
       for (const targetNode of targetNodes) {
         await db.query('RELATE $from->links_to->$to', {