Fix Invalid Date for API-created history records

[scowalt]

Summary

History records created via the MCP API (create_history_record / update_history_record) display "Invalid Date" on iOS Safari/WebKit.

Root cause: The date field in LiftohistoryDeserializer stores the raw Liftohistory text format:

"2026-02-28 10:45:30 +00:00"  (space separator)

iOS Safari's Date.parse() requires strict ISO 8601 with the T separator and returns NaN for space-separated date strings, causing "Invalid Date" in the UI.

Fix: Use parsedDate.toISOString() (which is already a correctly parsed Date object on line 138) to store:

"2026-02-28T10:45:30.000Z"  (strict ISO 8601)

This matches what the app stores when creating records through the normal UI flow (Program.createHistory, Progress.changeDate).

Reproduction

1. Create a history record via the MCP API:

   2026-03-29T01:37:57Z / duration: 1800s / exercises: {
     Bench Press / 3x8 185lb
   }
   

2. View the record in the Liftosaur iOS app
3. The workout date displays as "Invalid Date"

Change

One-line change in src/liftohistory/liftohistoryDeserializer.ts:

-    date: dateStr,
+    date: parsedDate.toISOString(),

[scowalt]

I generated this with Claude Code but it reflects a real issue I've been having, lmk if you have concerns or if anything is unclear