feat: prepare v1.2.0 server management and persistent TUI

[cotore-game]

Summary

• Make data/server.properties authoritative for new and migrated servers. Provide CLI and TUI migration, import, all-key editing, backup and restore.
• Add confirmed server deletion and a persistent TUI session with centered, aligned, resize-aware menus.
• Route common property edits through the same guarded backup path.
• Prepare VERSION 1.2.0 and English/Japanese usage docs.

Verification

• Local specification tests: 203 passed; one nested-ZIP test skipped because zip is not installed in the local WSL distro.
• Local Python TUI/property tests, locale validation and Bash syntax passed.
• GitHub Actions run 36699378925 passed Bash/Python syntax, locale validation, ShellCheck and the full specification suite.
• Real Docker Compose responds in WSL2. No user server data was modified.

Before merge

• Validate the interactive UI and representative create/migrate/restore/delete flows on WSL2 using disposable test data.
• Review the final release notes and confirm the v1.2.0 scope.
• Keep this PR as a draft. Do not merge yet.