chore: acquire-core migration monorepo (legacy C + Spring Boot target skeleton)

TxCore/ECPG legacy 매입·정산 C 슬라이스(빌드검증) + Spring Boot 멀티모듈 골격(mvn test green) + MIGRATION.md 전환룰 + CI(boot 빌드).

legacy/app/common/util_amount.c

@@ -0,0 +1,82 @@
+/*
+ * util_amount.c - 금액/통화 유틸리티 (plain C)
+ */
+#include "acq_util.h"
+
+#include <string.h>
+#include <ctype.h>
+#include <stdio.h>
+
+/* 거래금액 상한 (원). 건당 1억원 */
+#define AMOUNT_MAX  100000000L
+
+long amount_parse(const char *field, int len)
+{
+    long v = 0;
+    int  i;
+
+    if (!field || len <= 0)
+        return -1;
+
+    for (i = 0; i < len; i++) {
+        char c = field[i];
+        if (c == ' ')            /* 선행 공백 허용 */
+            continue;
+        if (!isdigit((unsigned char)c))
+            return -1;
+        v = v * 10 + (c - '0');
+    }
+    return v;
+}
+
+int amount_format(long amount, char *out, int len)
+{
+    char tmp[32];
+    int  n;
+
+    if (!out || len <= 0 || amount < 0)
+        return -1;
+
+    n = snprintf(tmp, sizeof(tmp), "%0*ld", len, amount);
+    if (n < 0 || n > len)        /* 폭 초과 = 오버플로우 */
+        return -1;
+
+    memcpy(out, tmp, len);       /* 널 종료 없이 고정폭 복사 */
+    return 0;
+}
+
+void amount_format_won(long amount, char *out, int outlen)
+{
+    char raw[32];
+    int  n, i, j, digits, first;
+
+    if (!out || outlen <= 0)
+        return;
+
+    n = snprintf(raw, sizeof(raw), "%ld", amount);
+    if (n < 0) {
+        out[0] = '\0';
+        return;
+    }
+
+    first = (raw[0] == '-') ? 1 : 0;
+    digits = n - first;
+
+    j = 0;
+    if (first && j < outlen - 1)
+        out[j++] = '-';
+
+    for (i = first; i < n && j < outlen - 1; i++) {
+        int pos = i - first;      /* 0-based 자릿수 위치 */
+        if (pos > 0 && (digits - pos) % 3 == 0)
+            if (j < outlen - 1)
+                out[j++] = ',';
+        out[j++] = raw[i];
+    }
+    out[j] = '\0';
+}
+
+int amount_is_valid(long amount)
+{
+    return (amount >= 1 && amount <= AMOUNT_MAX) ? 1 : 0;
+}