feat(account): 대출 실행금액 필드 추가 + 상환방식별 자동계산 분기

- loan_amount(대출 실행 금액) 컬럼 추가(DB/도메인/DTO/mapper)
- 계좌 폼: 대출 실행 금액 입력 / 기록 시작 시 잔액(기존 openingBalance) 레이블 분리
- 계좌 카드: 실행금액·금리·상환방식 표시
- 상환 자동계산 3방식 분기:
  - 원리금균등: 납입금액 입력 → 이자(잔액×월이율) / 원금(납입-이자) 분리
  - 원금균등: 실행금액÷기간=월원금, 잔액×월이율=이자 자동계산
  - 만기일시: 잔액×월이율=이자만 자동계산, 원금 0
- 자동계산 후 이자·원금 수동 조정 가능

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/views/account/AccountWalletView.vue

@@ -34,6 +34,7 @@ const form = reactive({
   openingDate: '',
   currentValue: null,
   // 대출(LOAN) 전용
+  loanAmount: null,
   loanRate: null,
   loanMethod: '',
   loanMonths: null,
@@ -201,7 +202,7 @@ function issuerLabel(t) {
   return t === 'BANK' ? '은행명' : t === 'CARD' ? '카드사' : t === 'INVEST' ? '증권사' : '대출기관'
 }
 function openingLabel(t) {
-  return t === 'BANK' || t === 'CASH' ? '초기 잔액' : t === 'CARD' ? '초기 미결제 금액' : t === 'INVEST' ? '투자금(투입원금)' : '대출 잔액(원금)'
+  return t === 'BANK' || t === 'CASH' ? '초기 잔액' : t === 'CARD' ? '초기 미결제 금액' : t === 'INVEST' ? '투자금(투입원금)' : '기록 시작 시 잔액'
 }
 // 투자 수익률(%) — 투입원금 대비 평가손익
 function returnPct(w) {
@@ -234,6 +235,7 @@ function openCreate() {
     openingBalance: 0,
     openingDate: '',
     currentValue: null,
+    loanAmount: null,
     loanRate: null,
     loanMethod: '',
     loanMonths: null,
@@ -254,6 +256,7 @@ function openEdit(w) {
     openingBalance: isLiability(w.type) ? -(w.openingBalance || 0) : w.openingBalance || 0,
     openingDate: w.openingDate || '',
     currentValue: w.currentValue ?? null,
+    loanAmount: w.loanAmount ?? null,
     loanRate: w.loanRate ?? null,
     loanMethod: w.loanMethod || '',
     loanMonths: w.loanMonths ?? null,
@@ -285,6 +288,7 @@ async function submit() {
       form.type === 'INVEST' && form.currentValue !== '' && form.currentValue != null
         ? Number(form.currentValue)
         : null,
+    loanAmount: isLoan && form.loanAmount ? Number(form.loanAmount) : null,
     loanRate: isLoan && form.loanRate !== null && form.loanRate !== '' ? Number(form.loanRate) : null,
     loanMethod: isLoan && form.loanMethod ? form.loanMethod : null,
     loanMonths: isLoan && form.loanMonths ? Number(form.loanMonths) : null,
@@ -383,8 +387,9 @@ onBeforeUnmount(() => sortable?.destroy())
                 >{{ revealedAccts.has(w.id) ? '🙈' : '👁' }}</button>
               </template>
               <template v-if="w.type === 'INVEST'"> · 투자금 {{ won(w.investedAmount) }}</template>
-              <template v-if="w.type === 'LOAN' && w.loanRate">
-                · {{ w.loanRate }}% <span v-if="w.loanMethod">/ {{ loanMethodLabel(w.loanMethod) }}</span>
+              <template v-if="w.type === 'LOAN'">
+                <span v-if="w.loanAmount"> · 실행 {{ won(w.loanAmount) }}원</span>
+                <span v-if="w.loanRate"> · {{ w.loanRate }}%<span v-if="w.loanMethod"> / {{ loanMethodLabel(w.loanMethod) }}</span></span>
               </template>
             </span>
           </div>
@@ -484,6 +489,10 @@ onBeforeUnmount(() => sortable?.destroy())
 
               <!-- 대출 전용 -->
               <template v-if="form.type === 'LOAN'">
+                <label>대출 실행 금액(원금)
+                  <input v-model.number="form.loanAmount" type="number" min="0"
+                    placeholder="처음 빌린 금액 (예: 10000000)" :disabled="submitting" />
+                </label>
                 <label>연이자율(%)
                   <input v-model.number="form.loanRate" type="number" min="0" max="100" step="0.01"
                     placeholder="예: 5.25" :disabled="submitting" />