Fix CSV export hang and OOM for large log files

[HarryWeppner]

Summary

Fixes #366. Two compounding bugs caused the app to become unresponsive when exporting large log files as CSV:

• The OOM: generateCsvTable() built a massive string[][] array using O(n) findIndex scans, then postMessage failed with DataCloneError trying to clone the result back to the main thread
• The hang: WorkerManager had no onerror or timeout handling, so when the worker crashed the promise never settled and the UI showed a loading indicator forever

Changes

• Rewrite generateCsvTable to use row-major iteration with advancing cursors and batched UTF-8 encoding, drastically reducing peak memory
• Transfer Uint8Array result via postMessage zero-copy (transferable) instead of cloning a string
• Add upperBound() binary search utility to replace O(n) findIndex in all four export functions (CSV table, CSV list, WPILOG, MCAP)
• Add worker.onerror handler and heartbeat timeout to WorkerManager so silent worker crashes reject the promise and show an error dialog
• Quote CSV column headers and key/value fields per RFC 4180

Test plan

• Export a large log file (~2500 fields, ~400K timestamps) as CSV (Table) — should complete without hanging or OOM
• Export as CSV (List) — verify key and value columns are properly quoted
• Export as WPILOG and MCAP with fixed-period sampling — verify output correctness
• Kill a worker mid-export — verify the app shows an error dialog instead of hanging
• Verify npm run compile and npm run check-format pass on source files