feat: click a coin row to view its trade history; edit transactions

Matches CoinMarketCap's flow: clicking anywhere on a coin's row in the
holdings table opens its transaction history (previously only a dedicated
icon button did). The table's own History icon is gone since the row now
does that job; the remaining "+"/delete icons get stopPropagation so they
don't also trigger the row click.

Adds the missing piece: transactions could be viewed and deleted but not
edited. New PATCH /crypto/transactions/{id} (partial update, never calls
CoinGecko, same oversell guard as creating a sell) backs a pencil button on
each history row that opens CryptoTransactionModal pre-filled — the same
dialog used for "+", now doing double duty as create/edit.

86/86 backend tests passing (4 new). Verified live against the real API:
create, edit quantity/note, 404 on unknown id, cleanup — real user data
untouched throughout.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01855PiW5Wd8n4aRW4n9kByY

frontend/src/pages/CryptoPage.tsx

@@ -11,7 +11,7 @@ import { CryptoTransactionModal } from "@/components/crypto/CryptoTransactionMod
 import { useCryptoHistory, useCryptoHoldings, useDeleteCryptoHolding, useRefreshCryptoPrices } from "@/hooks/useCrypto";
 import { getIntlLocale } from "@/lib/format";
 import { useTranslation } from "@/lib/i18n";
-import type { CryptoHolding, CryptoRange } from "@/types";
+import type { CryptoHolding, CryptoRange, CryptoTransaction } from "@/types";
 
 function formatSyncedAt(iso: string): string {
   return new Intl.DateTimeFormat(getIntlLocale(), { dateStyle: "medium", timeStyle: "short" }).format(new Date(iso));
@@ -33,6 +33,11 @@ export function CryptoPage() {
   const [addOpen, setAddOpen] = useState(false);
   const [tradingHolding, setTradingHolding] = useState<CryptoHolding | null>(null);
   const [historyHolding, setHistoryHolding] = useState<CryptoHolding | null>(null);
+  // Set together with tradingHolding when editing an entry from the history
+  // list — CryptoTransactionModal is the same dialog for both "+" (new
+  // trade, transaction stays null) and this (pre-filled, PATCHes instead of
+  // POSTing). Cleared whenever that dialog closes, same as tradingHolding.
+  const [editingTransaction, setEditingTransaction] = useState<CryptoTransaction | null>(null);
 
   const holdings = data?.holdings ?? [];
   const totalValue = holdings.reduce((sum, holding) => sum + (holding.value !== null ? Number(holding.value) : 0), 0);
@@ -43,6 +48,22 @@ export function CryptoPage() {
     }
   }
 
+  function handleEditTransaction(transaction: CryptoTransaction) {
+    setEditingTransaction(transaction);
+    setTradingHolding(historyHolding);
+    setHistoryHolding(null);
+  }
+
+  function closeTradeModal() {
+    setTradingHolding(null);
+    setEditingTransaction(null);
+  }
+
+  function openTradeModal(holding: CryptoHolding) {
+    setEditingTransaction(null);
+    setTradingHolding(holding);
+  }
+
   return (
     <div className="space-y-5">
       <CryptoOverviewCard
@@ -89,7 +110,7 @@ export function CryptoPage() {
               <CryptoHoldingsTable
                 items={holdings}
                 hidden={hidden}
-                onTrade={setTradingHolding}
+                onTrade={openTradeModal}
                 onViewHistory={setHistoryHolding}
                 onDelete={handleDelete}
               />
@@ -99,12 +120,18 @@ export function CryptoPage() {
       </Card>
 
       <CryptoAddModal open={addOpen} onClose={() => setAddOpen(false)} />
-      <CryptoTransactionModal open={tradingHolding !== null} onClose={() => setTradingHolding(null)} holding={tradingHolding} />
+      <CryptoTransactionModal
+        open={tradingHolding !== null}
+        onClose={closeTradeModal}
+        holding={tradingHolding}
+        transaction={editingTransaction}
+      />
       <CryptoTransactionHistoryModal
         open={historyHolding !== null}
         onClose={() => setHistoryHolding(null)}
         holding={historyHolding}
         hidden={hidden}
+        onEdit={handleEditTransaction}
       />
     </div>
   );