Add --exclude to skip projects by path glob - #21

Adds a repeatable --exclude / -x option to collect. It skips every GitLab project whose path matches a glob.

• Matching uses fnmatch.fnmatchcase on the full project path. * also matches /, so team/* drops projects in subgroups too.
• A --project path that matches is dropped before it is fetched. An excluded project that is misspelled or missing no longer stops the run.
• Group listings are filtered after GitLab returns them.
• With --jira, linked projects that match are dropped before any request is made for them. Each issue's link list in the Jira state still names them; only their service entries are removed.
• Excluded projects are left out of the report entirely, so the schema stays at 4.