feat: sortable columns on all dashboard tables

[maxdraki]

Request

Add clickable column sorting to the data tables across the dashboard UI.

Tables to cover

• Cron Monitoring (/crons) — sort by: Job, Last Status, Last Run, Avg Duration, Success Rate, Total Runs, Consec. Errors
• Traces (/traces) — sort by: Name, Status, Duration, Started At
• Models (/models) — sort by: Model, Requests, Tokens, Cost, p50/p95 Latency
• Health — sort by: Check, Status, Last Checked
• Logs — sort by: Level, Timestamp, Message

Implementation

Client-side JS sort (no server round-trip needed — data is already loaded):

1. Add data-sort attributes to <th> elements identifying the sort key and type (string, number, date)
2. On click: toggle asc/desc, re-sort the <tbody> rows by the column value, update a sort indicator (▲▼) in the header
3. Persist sort state in sessionStorage per table so it survives the 10s auto-refresh
4. Default sort per table:
   • Crons: Last Run descending (most recent first)
   • Traces: Started At descending
   • Models: Total Requests descending

UX notes

• Sort indicator should be visible but subtle (inline ▲▼ next to column label)
• Clicking the same column again reverses order
• Unsorted state not needed — always show a sort direction
• Should work alongside the existing 10s auto-refresh (re-apply current sort after data reload)