Fix Mizuho Bank branch names to match official website

Update branch names to match Mizuho Bank's official published names:
- Branch 649: PayPayカード → ナンテン
- Branch 692: PayPayカード第二 → アケビ

Fixes #28

Co-Authored-By: Claude Sonnet 4.5 <[email protected]>

Author: matsubo

data/branches/0001.json

@@ -2724,10 +2724,10 @@
   },
   "649":{
     "code":"649",
-    "name":"ＰａｙＰａｙカード",
-    "kana":"ペイペイカ－ド",
-    "hira":"ぺいぺいか－ど",
-    "roma":"peipeika-do"
+    "name":"ナンテン",
+    "kana":"ナンテン",
+    "hira":"なんてん",
+    "roma":"nanten"
   },
   "650":{
     "code":"650",
@@ -2899,10 +2899,10 @@
   },
   "692":{
     "code":"692",
-    "name":"ＰａｙＰａｙカード第二",
-    "kana":"ペイペイカ－ドダイニ",
-    "hira":"ぺいぺいか－どだいに",
-    "roma":"peipeika-dodaini"
+    "name":"アケビ",
+    "kana":"アケビ",
+    "hira":"あけび",
+    "roma":"akebi"
   },
   "693":{
     "code":"693",