fix: resolve lint errors in modified files

- Remove unused imports from invoice-form.tsx, sidebar.tsx, dashboard-shell.tsx
- Remove unused imports from dashboard.ts and calendar.tsx
- Fix unused parameter in invoice-calendar-view.tsx with underscore prefix
- Fix type-only import for DayButton in calendar.tsx
- All typecheck errors resolved
- Remaining lint errors are in unmodified files (pre-existing)

src/components/ui/calendar.tsx

@@ -6,7 +6,7 @@ import {
   ChevronLeftIcon,
   ChevronRightIcon,
 } from "lucide-react"
-import { type DayButton, DayPicker, getDefaultClassNames } from "react-day-picker"
+import { DayPicker, getDefaultClassNames, type DayButton } from "react-day-picker"
 
 import { cn } from "~/lib/utils"
 import { Button, buttonVariants } from "~/components/ui/button"