Fix dashboard timer polling loop and sync updates

[Fingolfin7]

Motivation

• The app polls the server for active timers so CLI-driven start/stop shows up in the UI, but the dashboard/home pages were reloading repeatedly because the polling logic assumed timer elements used id="timer-<id>" while the dashboard rendered different markup.
• The reload loop made the home/dashboard not reflect new timers correctly and not remove stopped timers, so polling needed to compare IDs reliably and avoid forcing reloads when unnecessary.

Description

• Updated dynamic_timers.js to use data-timer-id instead of parsing id="timer-<id>" by changing the selector to '#active-timers [data-timer-id]' and reading data('timer-id') in getLocalTimerIds().
• Added DASHBOARD_PATH + guard logic in syncActiveTimers() so when the active-timers container is not present the page only reloads once if the server reports active timers (avoids reload loops when the dashboard initially has no timers).
• Marked the dashboard active timers container as a partial list with `data-partial-list=

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Codex Task