feat: Application tracker status states — complete lifecycle (Closes #40)

[laurentketterle-hub]

Implements application tracker for NeraJob #40 (100 MRG).

Files added:

• nerajob/tracker.py — ApplicationTracker class with:
  • 14 status states (SAVED→APPLIED→SCREENING→...→ARCHIVED)
  • Validated state transition machine
  • Application timeline/history tracking
  • Aggregate statistics (response rate, offers, active count)
  • JSON export with stats

Usage:

from nerajob.tracker import ApplicationTracker, Application, ApplicationStatus
tracker = ApplicationTracker()
app = Application(id='1', job_id='j1', job_title='Engineer', company='Acme')
app.transition(ApplicationStatus.APPLIED, 'Submitted via Lever')
tracker.add(app)
print(tracker.stats())

[laurentketterle-hub]

/claim