[SandObserver]

Summary

• Add a githubService select (GitHub, Gitea, Forgejo, GitLab) and a githubUrl field to the github widget; rename its picker label to Git. Existing configs without a service read GitHub.
• Gitea and Forgejo: open pull requests from /api/v1/repos/issues/search (token owner filters, total from X-Total-Count), and the contribution grid from /api/v1/users/{user}/heatmap. The data reply carries the last year's slots as [seconds, count] pairs; the page sums them per day in the browser's time zone with the new ui/js/contribution-calendar.js.
• GitLab: open merge requests from /api/v4/merge_requests with scope=all and author, assignee or reviewer username filters, total from X-Total. Hide the View pills and the Mentioned filter for GitLab; a saved contributions view fails as a setup error.
• A server address without a scheme is read and linked over https.
• Per-service token hints, card label "Merge requests" and "Merge request filters" for GitLab, in all six locales.
• Add withManifestDefaults (api/src/widget-defaults.js): absent non-cosmetic fields take their manifest default, top level and one row deep. widgetConfigMatchesSaved and getWidgetData both read configs through it, so a config saved before a defaulted field keeps its stored secret when the editor sends the default.
• fetchJSON returns response headers only with withHeaders: true.
• The contributions page takes its link from profileUrl in the data reply instead of reading the widget config.

Testing
All green, including e2e. Added 33 tests for the Gitea, Forgejo and GitLab paths, manifest defaults, secret scope, the calendar across time zones, opt-in headers and token scope.

Changelog

Added

• Read pull requests and contributions from Gitea and Forgejo, and merge requests from GitLab, in the Git widget.

Changed

• Rename the GitHub widget to Git.

Checklist

• Stays within the project constraints: one container, no runtime dependencies, no build step (see CONTRIBUTING.md).
• Tests added or updated for new logic, and the full suite, lint, and typechecks pass.
• Docs updated if behavior or configuration changed.