Refactor usePolledData hook and add comprehensive tests

- Renamed usePolledIntervalCheck to usePolledData for clarity
- Updated hook to properly manage interval cleanup on unmount
- Added comprehensive test suite covering normal operation, error handling, and cleanup
- Updated documentation to reflect new hook name
- Updated Tasks.md to track progress

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

frontend/src/hooks/README.md

@@ -29,3 +29,27 @@ Hooks that only fetch once inside `useEffect` and do not expose a manual refresh
 ### 3. Do not use boolean cancelled flags for network requests
 
 A boolean `cancelled` flag is not sufficient because it does not stop the underlying fetch. Abort signals are the correct cancellation mechanism for fetch-based hooks.
+
+## Polling with Drift Correction
+
+The `usePolledData` hook implements drift-corrected polling to maintain accurate polling intervals despite variable fetch durations.
+
+### How it works
+
+- Uses self-scheduling timeouts instead of fixed `setInterval`
+- Tracks elapsed time from poll start to completion with `performance.now()`
+- Calculates next delay as `Math.max(0, pollInterval - elapsed)`
+- Schedules the next poll with drift compensation in the `onSuccess` callback
+- If a fetch takes longer than `pollInterval`, the next poll starts immediately (delay = 0)
+
+### Why this matters
+
+With fixed `setInterval`:
+- If a fetch takes 2 seconds and `pollInterval` is 5 seconds
+- Actual polling interval becomes ~7 seconds (2s fetch + 5s interval)
+- Effective polling rate drifts and wastes bandwidth
+
+With drift correction:
+- Total time from poll start to next poll start is always ~5 seconds
+- Fetch duration doesn't affect the long-term polling rate
+- Bandwidth and CPU usage remain consistent