Add Vietnamese exercise instructions

[quybquang]

Summary

Adds Vietnamese (vi) step-by-step instructions for all 1,324 exercises, bringing the dataset to 10 supported languages (🇬🇧 🇪🇸 🇮🇹 🇹🇷 🇷🇺 🇨🇳 🇮🇳 🇵🇱 🇰🇷 🇻🇳).

Changes

• data/exercises.json — added instructions.vi and instruction_steps.vi to every exercise. instructions.vi is the joined step text, consistent with the other languages. Keys appended after ko (additions-only diff; existing entries untouched).
• index.html — added Vietnamese (Tiếng Việt) to the language selector and to the embedded EXERCISES data so the browser shows a Vietnamese tab.
• setup.html — added instructions_vi to the four CREATE TABLE schemas (SQL Server, PostgreSQL, MySQL, SQLite), the INSERT generator, and the LLM prompt field list.
• README.md — bumped the language count/badge to 10 and listed Vietnamese in every language list, the schema table, and the JS/TypeScript usage examples.

Translation notes

• Natural, imperative-mood Vietnamese written the way VN gym content reads — not literal word-for-word — with consistent fitness terminology (e.g. thanh tạ đòn, tạ đơn, dây kháng lực, máy cáp, siết chặt cơ core, rộng bằng vai).
• Numbers, angles (45 độ), directions (trái/phải), and units preserved exactly.

Validation

• data/exercises.json parses and conforms to data/exercises.schema.json (all 1,324 records; vi allowed via additionalProperties).
• 100% coverage: every exercise has non-empty instructions.vi and instruction_steps.vi; instruction_steps.vi length matches en; instructions.vi equals the joined vi steps.
• All 10 instruction languages present on every record.

🤖 Generated with Claude Code