feat: add click-based colorized output with progress events and build timer

- Add click as explicit dependency (already bundled with typer)
- Replace typer.echo calls with click.echo + click.style for colorized output
- Add BuildEvent enum and ProgressCallback to builder for decoupled progress reporting
- Remove direct typer dependency from builder module
- Show per-target status with colored labels (skip/ok/fail/...)
- Display elapsed build time in summary
- Colorize graph and clean command output
- Update CLI tests to match new output format

pyproject.toml

@@ -5,6 +5,7 @@ description = "Bulk-Generate Images with Generative AI"
 readme = "README.md"
 requires-python = ">=3.13"
 dependencies = [
+    "click>=8.0.0",
     "httpx>=0.27.0",
     "mistralai>=1.0.0",
     "networkx>=3.6.1",