fix(schaledb): use JP student source

[HU-Lee]

Summary

• Use the Japanese SchaleDB dataset as the authoritative student roster and structure.
• Populate KO, JP, EN, and ZH student, skill, weapon, and gear names from each exact locale dataset.
• Reject incomplete or inconsistent locale sets before writing data; no locale fallback is used.
• Clarify the batch CLI role in the README.

Evidence

• Current upstream dry run: 270 students in every locale, zero ID differences, zero missing localized names across students, skills, selectable EX skills, weapons, and gear.
• Static checks, tests, and build: PASS.

Upstream status

Student 10148 is not present in any of the four current SchaleDB locale datasets yet. The batch can ingest it once SchaleDB publishes the record.

[HU-Lee]

After additional analysis, it's totally same.
Student 10148 is not present so I opened this PR, but this student (Iroha swimsuit) is updated 08/05 so not updated in SchaleDB.

Close the issue because this PR doesn't change anything.