Fix systemd service to use uv with full path

Updated service to use uv run with absolute path to avoid
PATH issues in systemd environment.

Service file changes:
- ExecStart: Uses absolute path to uv (/home/berwn/.local/bin/uv)
- Runs: uv run --no-project python rotary_phone_web.py
- This ensures uv manages dependencies correctly

Install script improvements:
- Auto-detects uv location with 'which uv'
- Falls back to $HOME/.local/bin/uv if not in PATH
- Validates uv exists before proceeding
- Substitutes actual uv path into service file
- Shows detected uv path in output

This fixes:
  ModuleNotFoundError: No module named 'waitress'

Now uv properly manages the virtual environment and
dependencies are available to the service.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

wedding-phone.service

@@ -9,7 +9,7 @@ User=berwn
 Group=berwn
 WorkingDirectory=/home/berwn/wedding-phone
 Environment="PATH=/home/berwn/.local/bin:/usr/local/bin:/usr/bin:/bin"
-ExecStart=/usr/bin/python3 rotary_phone_web.py
+ExecStart=/home/berwn/.local/bin/uv run --no-project python rotary_phone_web.py
 Restart=always
 RestartSec=10