fix: truncate creator profile fields by bytes

[pengyuayn]

Summary

• Adds truncateToBytes(value, maxBytes) for UTF-8 byte-safe string truncation.
• Applies byte-safe truncation before creator profile fields are persisted.
• Extends tests for ASCII, empty strings, multi-byte character boundaries, and creator profile write normalization.

Closes #556

Testing

• ./node_modules/.bin/jest src/utils/string-truncate.utils.test.ts src/modules/creator/creator-profile.service.test.ts --runInBand (18 tests passed)
• ./node_modules/.bin/eslint src/utils/string-truncate.utils.ts src/utils/string-truncate.utils.test.ts src/modules/creator/creator-profile.service.ts src/modules/creator/creator-profile.service.test.ts
• ./node_modules/.bin/prettier --check src/utils/string-truncate.utils.ts src/utils/string-truncate.utils.test.ts src/modules/creator/creator-profile.service.ts src/modules/creator/creator-profile.service.test.ts
• ./node_modules/.bin/tsc -p tsconfig.json --noEmit currently fails on existing Prisma generated-client/model typing issues across unrelated modules after local install/generate, e.g. missing creatorProfile, user, webhook model properties on the Prisma client.

Notes

• The repository pre-commit hook invokes pnpm install/status and is blocked locally by ignored build-script approvals for Prisma and other native dependencies. The targeted checks above were run directly.