[2022117144]

Summary

Closes #13.

Finish wiring the already-present Pydantic BaseSettings configuration through the actual backend. Previously the primary API still hard-coded its database path and title, discovery and alerts repeated hard-coded database defaults, and app/config.py imported BaseSettings directly from pydantic (which raises on Pydantic v2).

Code changes

• Use settings.app_name and settings.db_path in the real app.main entry point, and remove the invalid Device import from app.models.
• Use the same DB path from settings in ARP discovery and alert rules while preserving optional explicit caller overrides. Alert rules use configured Telegram destination by default.
• Support pydantic.v1.BaseSettings (available under Pydantic 2 and recent Pydantic 1) with a fallback for older v1 installs.
• Add .env.example, .gitignore (prevents real local secrets, SQLite files and caches from being committed), requirements.txt (also fills a file expected by the existing Dockerfile), and docs/CONFIGURATION.md.
• Add six focused regression tests covering defaults, typed environment variables, bad values, .env vs env precedence, API configuration and ARP discovery DB path overrides.

Verification

Windows / Python 3.10 / Pydantic 2.13.4, with python-dotenv installed:

• python -m pytest -q -p no:cacheprovider tests/test_config.py: 6 passed, four existing FastAPI on_event deprecation warnings (not introduced by this patch).
• python -m flake8 app/config.py app/main.py app/autodiscover.py app/alertrules.py tests/test_config.py --select=E9,F63,F7,F82 --show-source: exit 0.
• git diff --cached --check: exit 0.

The upstream CI still uses Python 3.9 although other existing modules use str | None annotations; a separate focused PR #34 already addresses the upstream CI test/tooling configuration. I have not represented this PR's GitHub-hosted checks as passing until they execute.

AI-assisted contribution under a human-operated GitHub account. No payout or bounty approval claimed.