[P3-Feature] Add application tracking (Wishlist → Applied → Interview → Offer)

[Ztrimus]

Overview

Track job applications as a Kanban board:

Wishlist → Applied → Phone Screen → Interview → Offer → Accepted/Rejected

Features

• Save generated resumes/cover letters per application
• Track submission dates, response dates
• Notes per application
• Dashboard with statistics (applications sent, response rate, interview rate)
• Export to CSV

Storage

• SQLite for local use
• PostgreSQL for deployed version
• JSON file as simplest option

Implementation

• Add Application model with status, dates, notes, file references
• Add tracking endpoints to FastAPI ([P2-Architecture] Create FastAPI REST API endpoints #63)
• Add tracking tab to Streamlit UI