Fix project isolation: Make loadChatHistory respect active project sessions

- Modified loadChatHistory() to check for active project before fetching all sessions
- When active project exists, use project.sessions instead of fetching from API
- Added detailed console logging to debug session filtering
- This prevents ALL sessions from appearing in every project's sidebar

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

logs/chat-monitor/failure-1769076700992.json

@@ -0,0 +1,5 @@
+{
+  "sessionId": "session-1769076694479-fq4376a8e",
+  "failureType": "browser_sse_error",
+  "error": "[SSEClient] Connected to session session-1769076694479-fq4376a8e"
+}