fix: migrate to tailwind v4 and TS6, add oauth2 dashboard_host setting

- migrate Tailwind v3->v4 (postcss @tailwindcss/postcss, CSS-first @theme/@plugin/@custom-variant)
- fix TS6 build: ignoreDeprecations for baseUrl, react-day-picker v10 classNames, test type fixes
- add dashboard_host setting field with i18n

src/components/ui/calendar.tsx

@@ -70,7 +70,7 @@ function Calendar({
                         : "[&>svg]:text-muted-foreground flex h-8 items-center gap-1 rounded-md pl-2 pr-1 text-sm [&>svg]:size-3.5",
                     defaultClassNames.caption_label,
                 ),
-                table: "w-full border-collapse",
+                month_grid: "w-full border-collapse",
                 weekdays: cn("flex", defaultClassNames.weekdays),
                 weekday: cn(
                     "text-muted-foreground flex-1 select-none rounded-md text-[0.8rem] font-normal",