Add Graveyard XP recovery modes and localization

[remdui]

What changed

• add experience.mode with NATIVE and PERCENTAGE options
• default to NATIVE, storing the exact final PlayerDeathEvent#getDroppedExp() value after Minecraft and other death listeners have modified it
• keep experience.recovery_percentage for PERCENTAGE mode, clamped to 0..100 and rounded down
• route hologram titles, hologram timer states, tracking action bars, durations and grave status labels through the localization handler
• render hologram components per viewer so language selection is respected
• document the new XP policy and localization keys

Hardcoded text audit

Direct player-facing Graveyard runtime text now uses localization keys. Internal diagnostics, audit reasons and server log messages remain technical strings and are not shown as localized player UI.

Validation

• tests cover native XP preservation and percentage flooring/clamping
• timer tests cover second-precision duration decomposition after localization
• branch is based directly on current main, so the PR contains no duplicate changes from the already merged command argument fix