Make the dashboard a grid of projects with their inbox

DashboardView drops the placeholder for a full-width grid of project cards.
Each card links to the project and lists its inbox cards (status_id === null)
under a "New" heading, or "Nothing new." when empty. Cards are fetched per
project (one GET /projects/{id}/cards each) after the project list resolves.

projects store: fetchProjects() now shares one in-flight request between
concurrent callers (the sidebar and the dashboard mount together).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/README.md

@@ -52,9 +52,10 @@ it). The current page is highlighted via RouterLink's `active-class`.
 `<RouterView :key="route.path">` remounts the view on every path change so
 sidebar → project → project navigation always does a fresh load.
 
-`/` redirects to `/dashboard` (`DashboardView.vue`, an "under construction"
-placeholder). Signed-out routes (`/login`, `/register`, `/verify-email`) render
-without the sidebar.
+`/` redirects to `/dashboard` (`DashboardView.vue`), a full-width grid of
+project cards — each shows the project name and, under a **New** heading, its
+inbox cards (`status_id === null`), fetched per project. Signed-out routes
+(`/login`, `/register`, `/verify-email`) render without the sidebar.
 
 ## Project detail