feat(frontend): update sessions page for enhanced health monitoring

- Add new status badges: starting, probing, unhealthy
- Show tunnel error only when tunnel_status is unreachable
- Show app error badge with status code for error_response
- Add collapsible probe output section for diagnostics
- Update health polling to check all active instances
- Only show Recreate Tunnel button for unreachable tunnels

apps/api/src/models/tool_instance.py

@@ -2,7 +2,7 @@ import uuid
 from datetime import datetime
 from typing import TYPE_CHECKING
 
-from sqlalchemy import DateTime, ForeignKey, Integer, String
+from sqlalchemy import DateTime, ForeignKey, Integer, JSON, String
 from sqlalchemy import Uuid as UUID
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
@@ -62,6 +62,9 @@ class ToolInstance(UUIDPrimaryKeyMixin, TimestampMixin, Base):
     last_stopped_at: Mapped[datetime | None] = mapped_column(
         DateTime(timezone=True), nullable=True
     )
+    probe_result: Mapped[dict | None] = mapped_column(
+        JSON, nullable=True
+    )
 
     tool_type: Mapped["ToolType"] = relationship()
     repository: Mapped["GitRepository"] = relationship()