refactor: remove dead code identified by knip

Delete unused Fab component (superseded by QuickAddFab), unused server
actions and queries (listDashboards, reorderDashboards, deleteCareLog,
canAccessContainer, getOverduePlants, getCareDueSoon, addItemToDefaultList,
reorderItems, getOrCreateDefaultList), unused helpers (getCurrentUser,
BrandWordmark, TopbarSpacer, DEV_LOGIN_COOKIE, no-arg ensureDefault*
wrappers, addListItem re-export), and drop export keyword from five
internal-only functions.

Verified with typecheck, eslint, and production build after each removal.

src/modules/_core/reminders.ts

@@ -54,7 +54,7 @@ export async function listReminders(entityType: string, entityId: string) {
     .where(and(eq(reminders.entityType, entityType), eq(reminders.entityId, entityId)));
 }
 
-export async function tickReminders() {
+async function tickReminders() {
   let dueReminders: (typeof reminders.$inferSelect)[] = [];
 
   try {