Feat: Add Retirement Savings Breakdown Feature

[Azzbo77]

Adds the ability to break down retirement savings with a new card that allows users to manage individual items (e.g., pension accounts, investment accounts, savings).

Changes:

• New RetirementBreakdownCard component for CRUD operations on breakdown items
• Updated RetirementSavingsCard to display total (base amount + breakdown items) with real-time sync
• New toggle in Settings page to enable/disable the breakdown feature with help modal
• UIPreferencesContext enhanced to persist feature preference
• Dashboard now displays both retirement savings card (top) and breakdown card (bottom)
• Settings accessible from both Dashboard and Summary pages with correct navigation

[cachebag]

Very nice! Could you address CI?

[Azzbo77]

Fix frontend CI test failures

The linting checks were failing due to several issues in the retirement savings components:

RetirementBreakdownCard.tsx:

Fixed impure function warning by wrapping Date.now() in a helper function
Moved localStorage initialization from useEffect to useState lazy initializer
Replaced as any type casts with proper Event type checking
RetirementSavingsCard.tsx:

Fixed setState in effect by using useState lazy initializer for localStorage
Replaced as any type casts with proper Event type checking
ID Generation:

Updated to use Date.now().toString() for timestamp-based IDs (consistent with CustomSavingsGoals)
Note: Did not modify CustomSavingsGoals to match