feat: seed-based repo scanning + fork/private visibility flags

Replace the top-10-starred sampling with a seed list built from
contributionsCollection.commitContributionsByRepository, unioned across
every active contributionYear. Commit-history probes now land only on
repos where the user actually committed, covering all owned repos plus
forks and repos owned by others when allowed.

New visibility knobs (default off — public-facing READMEs stay
safe):
- -include-forks / include_forks    : include forked repos
- -include-private / include_private: include private repos (requires
                                      PAT with repo scope)

Compatibility:
- -top-repos default changed 10 → 0 (unlimited); still usable as a cap
  for fast local runs.
- commitHistoryQuery now takes $owner so probes can target forks or
  repos outside the user's ownership.
- FetchProfile now accepts FetchOptions; PublicRepos counts only repos
  that pass the visibility filter.

Seed-list approach mirrors github-profile-summary-cards' own repo
sourcing but keeps our byte-weighted commit attribution.

internal/github/productive.go

@@ -56,8 +56,12 @@ func (c *Client) FetchProductive(p *Profile, repos []RepoInfo, loc *time.Locatio
 			if seen >= maxPerRepo {
 				break
 			}
+			owner := repo.Owner
+			if owner == "" {
+				owner = p.Login
+			}
 			vars := map[string]any{
-				"login":  p.Login,
+				"owner":  owner,
 				"repo":   repo.Name,
 				"userId": p.ID,
 			}