Fix(web): expense details, dashboard currency formatting, and stale realtime copy

[Arun-kushwaha007]

• Add web expense detail view (mobile parity) #1 Add web expense detail view
• Dashboard summary uses USD regardless of group currency #4 Dashboard summary uses USD regardless of group currency
• Remove inaccurate realtime copy on dashboard/activity #6 Remove inaccurate realtime copy on dashboard/activity

Commits:

• 7157b72 feat(web): add expense detail page with receipt preview (Add web expense detail view (mobile parity) #1)
• 4436465 fix(web): correct dashboard currency and refresh copy (Dashboard summary uses USD regardless of group currency #4, Remove inaccurate realtime copy on dashboard/activity #6)

What changed:

• Add web expense detail view (mobile parity) #1: added a web expense detail route with receipt preview/upload support, linked expense rows to it, and
  exposed receiptFileKey in the expense DTO/backend response.
• Dashboard summary uses USD regardless of group currency #4: dashboard liabilities/assets now use the active group currency, and show — when no active group is
  selected.
• Remove inaccurate realtime copy on dashboard/activity #6: removed misleading “realtime” wording and replaced it with refresh-based copy.

Verification:

• pnpm --filter backend lint
• pnpm --filter web lint
• pnpm --filter backend test

Closes #1
Closes #4
Closes #6