Move new-project form to the dashboard; sidebar project list becomes a switcher; Kanban is the default project tab

- DashboardView: a "New project title" form now sits directly below the
  project grid (creating one stays on the dashboard -- the grid and the
  sidebar dropdown pick it up via the shared projects store, no navigation).
- AppSidebar: the per-project RouterLink list is replaced by a <select>. It's
  a v-model-bound writable computed (selectedProjectId): the getter tracks
  route.params.id so it reflects whichever project is open, the setter
  router.pushes to the chosen one -- so it doubles as a project switcher from
  anywhere, not just a picker from the dashboard. Removed the now-unused
  .sidebar__link--project/.sidebar__projects/.sidebar__form CSS; added
  .sidebar__select, and .form--new-project back for the dashboard form.
- ProjectView: activeTab now initialises to 'kanban' instead of 'all'. The
  tabs array (and so the tab bar's DOM order, All tasks first) is untouched --
  only the default selection changed.

Verified via headless Chrome: sidebar has no per-project links (a <select>
listing both projects instead); the new-project form follows the grid and
creating from it stays on /dashboard while the grid and dropdown both update;
selecting a project in the dropdown navigates there and the dropdown reflects
it once there; a project opens on Kanban with the tab bar still reading "All
tasks, Kanban" in that order.

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

web/src/style.css

@@ -158,9 +158,23 @@ body {
   color: var(--muted);
 }
 
-.sidebar__projects {
-  max-height: 45vh;
-  overflow-y: auto;
+.sidebar__select {
+  display: flex;
+  align-items: center;
+  gap: 0.6rem;
+  padding: 0.2rem 0.6rem;
+}
+
+.sidebar__select select {
+  flex: 1;
+  min-width: 0;
+  font: inherit;
+  font-size: 0.9rem;
+  padding: 0.35rem 0.4rem;
+  border: 1px solid var(--border);
+  border-radius: 6px;
+  background: var(--bg);
+  color: var(--text);
 }
 
 .sidebar__inbox-cards {
@@ -174,31 +188,6 @@ body {
   font-size: 0.85rem;
 }
 
-.sidebar__form {
-  display: flex;
-  flex-direction: column;
-  gap: 0.4rem;
-  margin-top: 1rem;
-  padding-top: 1rem;
-  border-top: 1px solid var(--border);
-}
-
-.sidebar__form input {
-  font: inherit;
-  font-size: 0.9rem;
-  padding: 0.4rem 0.55rem;
-  border: 1px solid var(--border);
-  border-radius: 6px;
-  background: var(--bg);
-  color: var(--text);
-}
-
-.sidebar__form button[type='submit'] {
-  padding: 0.45rem 0.7rem;
-  font-size: 0.9rem;
-  border-radius: 6px;
-}
-
 .card {
   background: var(--surface);
   border: 1px solid var(--border);
@@ -644,6 +633,7 @@ h1 {
   margin: 1.25rem 0;
 }
 
+.form--new-project,
 .form--new-card {
   margin-top: 1.5rem;
   padding-top: 1.25rem;