feat(ui): declutter dashboard done-recently + MCP-access, add per-project stats

Dashboard:
- 'Done recently' chip-cloud -> compact uniform list (Active-now row style),
  showing 5 with inline expand to the rest (backend already returns up to 8).
- New 'Projects' rail card: each active project with 'N open · M done'.
  Backend already computed done_count (dashboard.py) — now surfaced in the
  /api/dashboard payload per active project.

MCP Access (Connect Claude / Claude Code):
- Progressive disclosure: lead with the pre-filled plugin-install snippet;
  fold server name, scope, marketplace URL, and the MCP-only path into a
  single 'Customize' expander. Desktop tab keeps its own server-name field.
- Marketplace URL now defaults to this instance's own repo via
  config.PLUGIN_MARKETPLACE_URL (env-overridable); /api/plugin/marketplace-url
  falls back to it, so the field + install snippet are pre-filled out of the
  box instead of showing a generic placeholder.

Refs #761

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/scribe/services/dashboard.py

@@ -122,7 +122,8 @@ async def _active_projects(user_id: int) -> list[dict]:
             out.append({
                 "id": project.id, "title": project.title, "color": project.color,
                 "last_activity": (last or project.updated_at).isoformat(),
-                "open_count": open_count, "progress_pct": progress_pct,
+                "open_count": open_count, "done_count": done_count,
+                "progress_pct": progress_pct,
                 "milestones": milestones,
                 "no_milestone": [_task_row(t) for t in no_ms],
             })