feat(account): 대출 계좌 금리/상환방식 저장 + 상환 시 납입금액 자동분리

- wallet 테이블에 loan_rate/loan_method/loan_months/loan_start 컬럼 추가(ALTER TABLE)
- 대출 계좌 폼에 연이자율(%), 상환방식(원리금균등/원금균등/만기일시), 기간, 시작일 입력 필드 추가
- 계좌 목록에 금리·상환방식 표시
- 상환 폼: 금리 설정된 대출 계좌 선택 시 납입금액 입력 → 이자/원금 자동계산
  - 원리금균등/원금균등: 잔액 × 연이율/12 = 이자, 납입액-이자 = 원금
  - 만기일시상환: 납입액 전체 이자로 처리
  - 자동계산 후 수동 조정 가능

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

src/views/account/AccountWalletView.vue

@@ -33,6 +33,11 @@ const form = reactive({
   openingBalance: 0,
   openingDate: '',
   currentValue: null,
+  // 대출(LOAN) 전용
+  loanRate: null,
+  loanMethod: '',
+  loanMonths: null,
+  loanStart: '',
 })
 const submitting = ref(false)
 const formError = ref(null)
@@ -229,6 +234,10 @@ function openCreate() {
     openingBalance: 0,
     openingDate: '',
     currentValue: null,
+    loanRate: null,
+    loanMethod: '',
+    loanMonths: null,
+    loanStart: '',
   })
   formError.value = null
   formOpen.value = true
@@ -245,6 +254,10 @@ function openEdit(w) {
     openingBalance: isLiability(w.type) ? -(w.openingBalance || 0) : w.openingBalance || 0,
     openingDate: w.openingDate || '',
     currentValue: w.currentValue ?? null,
+    loanRate: w.loanRate ?? null,
+    loanMethod: w.loanMethod || '',
+    loanMonths: w.loanMonths ?? null,
+    loanStart: w.loanStart || '',
   })
   formError.value = null
   formOpen.value = true
@@ -258,6 +271,7 @@ async function submit() {
   }
   submitting.value = true
   const magnitude = Number(form.openingBalance) || 0
+  const isLoan = form.type === 'LOAN'
   const payload = {
     type: form.type,
     name: form.name.trim(),
@@ -271,6 +285,10 @@ async function submit() {
       form.type === 'INVEST' && form.currentValue !== '' && form.currentValue != null
         ? Number(form.currentValue)
         : 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,
+    loanStart: isLoan && form.loanStart ? form.loanStart : null,
   }
   try {
     if (editId.value) await accountApi.updateWallet(editId.value, payload)
@@ -297,6 +315,9 @@ async function remove(w) {
 function cardTypeLabel(v) {
   return v === 'CHECK' ? '체크' : v === 'CREDIT' ? '신용' : ''
 }
+function loanMethodLabel(v) {
+  return v === 'EQUAL_PAYMENT' ? '원리금균등' : v === 'EQUAL_PRINCIPAL' ? '원금균등' : v === 'BULLET' ? '만기일시' : ''
+}
 
 onMounted(async () => {
   await load()
@@ -362,6 +383,9 @@ 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>
             </span>
           </div>
           <div class="balance-wrap">
@@ -458,6 +482,29 @@ onBeforeUnmount(() => sortable?.destroy())
               </template>
               <label>기준일<input v-model="form.openingDate" type="date" :disabled="submitting" /></label>
 
+              <!-- 대출 전용 -->
+              <template v-if="form.type === 'LOAN'">
+                <label>연이자율(%)
+                  <input v-model.number="form.loanRate" type="number" min="0" max="100" step="0.01"
+                    placeholder="예: 5.25" :disabled="submitting" />
+                </label>
+                <label>상환방식
+                  <select v-model="form.loanMethod" :disabled="submitting">
+                    <option value="">(선택 안 함)</option>
+                    <option value="EQUAL_PAYMENT">원리금균등상환</option>
+                    <option value="EQUAL_PRINCIPAL">원금균등상환</option>
+                    <option value="BULLET">만기일시상환</option>
+                  </select>
+                </label>
+                <label>대출기간(개월)
+                  <input v-model.number="form.loanMonths" type="number" min="1"
+                    placeholder="예: 120 (10년)" :disabled="submitting" />
+                </label>
+                <label>대출시작일
+                  <input v-model="form.loanStart" type="date" :disabled="submitting" />
+                </label>
+              </template>
+
               <p v-if="formError" class="msg error">{{ formError }}</p>
 
               <div class="buttons">