Add canonical escrow status enum, analytics hook, wallet preference, filter params

[yusuftomilola]

Adds small, focused starter modules for four assigned issues, each as a new file:

• utils::escrowStatus::CanonicalEscrowStatus: single canonical status enum + normalizeEscrowStatus mapping legacy lowercase/uppercase variants to it. Updating StatusTabs/EscrowFilters/FilterBadges to import from here instead of comparing raw strings is a follow-up.
• hooks::useAdminAnalyticsVolume: React Query hook fetching real volume data from the backend analytics API, ready to replace the dashboard's hardcoded chart data. Loading skeletons and error/retry states are a follow-up.
• utils::walletPreference: localStorage helpers to save/read/clear the last connected wallet (Freighter/Albedo/Lobstr). Wiring the auto-reconnect prompt and Settings-page UI is a follow-up.
• utils::transactionFilterParams: serialize/parse helpers for date range + escrow + type filters as URL query params, plus an active-filter counter. Wiring into the transactions page filter bar and CSV/PDF export is a follow-up.

Closes #471
Closes #473
Closes #475
Closes #479

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