feat(timer): add workday timer with logging and sleep prevention

[alexandreprates]

feat(timer): add 9h workday menu bar timer with daily logging and no-sleep mode

• implement 9-hour countdown workday timer using SwiftBar plugin
• add persistent state management across executions
• add daily CSV logging (date, start time, end time)
• send macOS notification when workday completes
• prevent system sleep during active session using caffeinate
• add menu actions (start, reset, open log, open state directory)
• handle automatic reset after timer completion