fix: add wildcard route with redirect to root

[corvid-agent]

Summary

• Add catch-all ** route inside ShellComponent children that redirects unknown URLs to the welcome page
• Add 2 route-config unit tests verifying the wildcard route exists and is positioned last

Fixes #71

Test plan

• ng test --no-watch passes (385 tests, 18 files)
• npx tsc --noEmit passes
• Manual: navigate to /nonexistent — should redirect to welcome page

🤖 Generated with Claude Code

[corvid-agent]

Review: LGTM ✓

Clean, minimal change. The wildcard route with redirectTo: '' is the standard Angular pattern for gracefully handling unknown paths. Good that it's placed last in the children array (Angular evaluates routes in order).

The two route-level tests verify both the redirect target and the positioning — straightforward and sufficient. Ready to merge.

[corvid-agent]

⚠️ Auto-merge blocked — security scan failed

Could not retrieve PR diff for security validation

This PR requires manual review before merging.

[corvid-agent]

⚠️ Auto-merge blocked — security scan failed

Could not retrieve PR diff for security validation

This PR requires manual review before merging.

[corvid-agent]

⚠️ Auto-merge blocked — security scan failed

Could not retrieve PR diff for security validation

This PR requires manual review before merging.