VanguardClans - Advanced Clans System v1.5.9

Bump project version to 1.5.9
Replace TAB dependency artifactId/version (com.github.NEZNAMY: TAB -> TAB-API v5.5.0) as a provided dependency.
Make PAPI return a configurable no-clan placeholder instead of hardcoded "N/A": add getNoClanPlaceholder() and use it when player or clan is null, and add placeholders.no-clan-value to config.yml (and packaged resources).
Minor build property ordering adjusted in dependency-reduced-pom.

Add a clan slots item to the GUI with click handling to run "/clan slots buy" and display slot status, points, and next-upgrade info. Implement slot upgrade parsing and slot-limit calculation driven by new config options (clan-slots.* and gui.display templates). Add persistence checks after clan rename/tag updates in CCMD to verify storage changes and call a new VanguardClan.refreshClanVisuals() to reset nametag/tab hooks; throw IllegalStateException if updates are not persisted. Update H2/MySQL/SQLite SQL to use the renamed player_clan_history.clan column. Add language entries for the slots item and various Spanish text fixes, and update generated target resources accordingly.