Add ability to archive budgets

Keep your budget view clean by archiving old budgets without losing historical data.

Problem: Users accumulate irrelevant budgets (old projects, expired goals) with no way to hide them without deletion.

Solution:

• Archive/unarchive budgets from budget options

• Archived budgets hidden from main list by default

• Toggle/tab to view archived budgets when needed

• Visual distinction for archived items

• All budget data and history preserved

Implementation: Add “archived” boolean field to budgets table, backend endpoint for toggle, frontend UI for archive action and archived view.