v1.1.0 — Security and quality refactor

Security and code-quality refactor after the course, done before the public release.

Security

• Passwords are now hashed with bcrypt instead of being stored in plaintext
• Login/register responses no longer include the password field
• Login returns a uniform 401 for unknown users and wrong passwords
• Failed logins now return a JSON error (previously an empty response)
• Request validation added on the user model

Code quality

• Renamed system_stat_cotroller package to system_stat_controller
• Fixed router package name (routes -> router)
• SQLite connection pool limited to a single connection
• Server port is configurable via the PORT environment variable

Infrastructure

• Multi-stage Dockerfile for containerized deployment