refactor: replace config.yml with .env for all configuration

All settings (auth credentials, scanner ranges, status_checker interval)
now live in a single .env file via pydantic-settings. config.yml and
config.yml.example are deleted.

- Settings: add auth_username, auth_password_hash, scanner_ranges,
  status_checker_interval; add load_overrides()/save_overrides() for
  persisting runtime changes to data/scan_config.json
- auth.py: read credentials directly from settings
- scan.py: read ranges/interval from settings; write-back via save_overrides()
- scheduler.py: read interval directly from settings
- main.py: call settings.load_overrides() at startup
- docker-compose.yml: remove config.yml volume mount, add new env vars
- conftest.py: set settings fields directly instead of writing a temp config.yml

scripts/lxc-install.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 # Homelable — LXC/VM bootstrap installer
 # Compatible with Proxmox VE (Debian/Ubuntu LXC containers)
-# Usage: bash <(curl -fsSL https://raw.githubusercontent.com/you/homelable/main/scripts/lxc-install.sh)
+# Usage: bash <(curl -fsSL https://raw.githubusercontent.com/Pouzor/homelable/main/scripts/lxc-install.sh)
 
 set -euo pipefail
 
@@ -48,7 +48,7 @@ if ! id "$SERVICE_USER" &>/dev/null; then
 fi
 
 # ── Clone / update repo ───────────────────────────────────────────────────────
-REPO_URL="https://github.com/you/homelable.git"   # ← update before publishing
+REPO_URL="https://github.com/Pouzor/homelable.git"
 if [[ -d "$INSTALL_DIR/.git" ]]; then
   info "Updating existing installation..."
   git -C "$INSTALL_DIR" pull