Translate admin pages - Create admin.json files and translate all admin pages

- Create admin.json translation files for es, en, ca with all admin strings
- Update IntlProvider to include admin namespace
- Translate admin/invites/page.tsx - all strings now use translations
- Translate admin/trades/page.tsx - all strings now use translations
- Translate admin/price-history/page.tsx - all strings now use translations
- Translate admin/availability/page.tsx - all strings now use translations
- Add 'saving' key to common.json for all languages
- Fix linting errors: add t to useCallback dependencies
- All admin pages now fully multilingual

frontend/locales/en/admin.json

@@ -0,0 +1,113 @@
+{
+  "invites": {
+    "title": "Invites",
+    "createInvite": "Create Invite",
+    "godfatherLabel": "Godfather (user who can share this invite)",
+    "selectUser": "Select a user...",
+    "noUsersHint": "No users loaded yet. Create at least one invite to populate the list.",
+    "creating": "Creating...",
+    "allInvites": "All Invites",
+    "allStatuses": "All statuses",
+    "statusReady": "Ready",
+    "statusSpent": "Spent",
+    "statusRevoked": "Revoked",
+    "invitesCount": "{count} invites",
+    "tableHeaders": {
+      "code": "Code",
+      "godfather": "Godfather",
+      "status": "Status",
+      "usedBy": "Used By",
+      "created": "Created",
+      "actions": "Actions"
+    },
+    "noInvites": "No invites yet",
+    "revoke": "Revoke",
+    "errors": {
+      "loadFailed": "Failed to load invites",
+      "revokeFailed": "Failed to revoke invite"
+    }
+  },
+  "trades": {
+    "title": "Trades",
+    "subtitle": "Manage Bitcoin exchange trades",
+    "tabs": {
+      "upcoming": "Upcoming ({count})",
+      "history": "History ({count})"
+    },
+    "filters": {
+      "allStatuses": "All Statuses",
+      "completed": "Completed",
+      "noShow": "No Show",
+      "userCancelled": "User Cancelled",
+      "adminCancelled": "Admin Cancelled"
+    },
+    "searchPlaceholder": "Search by email...",
+    "loading": "Loading trades...",
+    "emptyStates": {
+      "upcoming": "No upcoming trades.",
+      "past": "No trades found."
+    },
+    "tradeDetails": {
+      "rate": "Rate:",
+      "market": "Market:",
+      "sellBtc": "SELL BTC",
+      "buyBtc": "BUY BTC",
+      "sendVia": "Send via {method}",
+      "receiveVia": "Receive via {method}",
+      "onchain": "Onchain",
+      "lightning": "Lightning",
+      "signal": "Signal: {value}"
+    },
+    "actions": {
+      "complete": "Complete",
+      "noShow": "No Show",
+      "cancel": "Cancel"
+    },
+    "errors": {
+      "loadUpcomingFailed": "Failed to load upcoming trades",
+      "loadPastFailed": "Failed to load past trades",
+      "actionFailed": "Failed to {action} trade"
+    }
+  },
+  "priceHistory": {
+    "title": "Bitcoin Price History",
+    "recordsCount": "{count} records",
+    "refresh": "Refresh",
+    "fetching": "Fetching...",
+    "fetchNow": "Fetch Now",
+    "tableHeaders": {
+      "source": "Source",
+      "pair": "Pair",
+      "price": "Price",
+      "timestamp": "Timestamp"
+    },
+    "loading": "Loading...",
+    "emptyState": "No price records yet. Click \"Fetch Now\" to get the current price."
+  },
+  "availability": {
+    "title": "Availability",
+    "subtitle": "Configure your available time slots for the next {days} days",
+    "copyMode": {
+      "hint": "Select days to copy to, then click Copy",
+      "copyTo": "Copy to {count} day(s)",
+      "copying": "Copying...",
+      "cancel": "Cancel"
+    },
+    "modal": {
+      "title": "Edit Time Slots",
+      "startTime": "Start Time",
+      "endTime": "End Time",
+      "addSlot": "Add Slot",
+      "removeSlot": "Remove",
+      "save": "Save",
+      "clear": "Clear",
+      "close": "Close",
+      "noAvailability": "No availability"
+    },
+    "errors": {
+      "saveFailed": "Failed to save",
+      "clearFailed": "Failed to clear",
+      "copyFailed": "Failed to copy"
+    }
+  }
+}