chore: remove .idea from tracking, add to .gitignore

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitignore

@@ -3,3 +3,4 @@ data/
 *.csv
 *.tmp
 .claude/
+.idea/

.idea/.gitignore

@@ -1,10 +0,0 @@
-# Default ignored files
-/shelf/
-/workspace.xml
-# Ignored default folder with query files
-/queries/
-# Datasource local storage ignored files
-/dataSources/
-/dataSources.local.xml
-# Editor-based HTTP Client requests
-/httpRequests/