feat: Automatic kanban.md reloading with visual highlights

[ljack]

This PR implements a real-time auto-reload feature for the Kanban board when changes are made to kanban.md on disk (e.g. by an external editor or script). It also introduces visual highlights to let users easily spot new or moved items.

Key Features

1. Background Polling Watcher:

   • Implements a background check loop (every 1000ms) in the File System Access integration.
   • Compares the lastModified timestamp and actual content text to reload kanban.md externally.
   • Refreshes open task detail views dynamically if they are open, or closes them if the task is deleted.
   • Safely updates the internal tracker during UI-driven saves (autoSave) to prevent self-triggering loops.

2. Auto-Reload UI Control:

   • Adds a checkbox toggle in the header bar (checked/enabled by default) next to the language selector.
   • Fully localized in English, French, German, and Chinese.

3. Visual Change Highlights:

   • When the file reloads, it compares the update against the previous tasks list in memory.
   • Newly added tasks flash with a green outline (task-card--new), and moved tasks flash with a blue outline (task-card--moved).
   • Highlight fades back smoothly to the standard style over 5 seconds via CSS keyframe animations.

[ioniks]

Hi

I have to check this pull request but I can't move back from 2.0 to 1.3.2 in release.

2.0 release have serious change in code from kanban.MD (integrate a migration)

[ljack]

Ah, sorry this is actually made againts master (didn't notice it was 2.0.0 already). Thought my AI was hallusinating ;) Reverted to version downgrade as this is actually made againts master (which seemed to be 2.0.0).