feat: chef commands moved to admin + PlaceholderAPI integration

Chef → admin: the chef role no longer grants any command privilege.
All team-management subcommands now take <team> as an argument and are
gated by their crcore.team.<action> permission only:
- add <team> <player>
- remove <team> <player>
- transfer <team> <player>
- visibility <team> <PUBLIC|PRIVATE>
- setspawn <team> (still player-only — needs admin's location)

The LEADER role is kept in the data model (Team / TeamMember) and remains
usable by game plugins via the API, but does not unlock any default
command. Future work can re-introduce chef-specific commands if needed.

PlaceholderAPI: auto-detected at CRCore.enable(). If the PAPI plugin is
present on the server, CRCorePlaceholderExpansion registers automatically;
otherwise the lib runs without it (no NoClassDefFoundError thanks to the
indirection through doRegisterPlaceholderHook).

Placeholders exposed:
- Team: %crcore_team%, %crcore_team_name/tag/color/color_chat/size/
  visibility/leader_name/total_score%, %crcore_team_score_<name>%
- Player: %crcore_player_score_<name>%, %crcore_player_score_total%

Dependency: me.clip:placeholderapi:2.11.6, scope provided. New repo:
https://repo.extendedclip.com/content/repositories/placeholderapi/.

docs/features.md, decisions.md and the builtin-commands diagram updated to
reflect the simpler admin/player two-tier model and the PAPI section.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

docs/setup.md

@@ -5,6 +5,7 @@
 - **Type** : librairie Java (`jar`) — pas un plugin Bukkit
 - **artifactId Maven** : `CR-Core`
 - **Build** : Maven, Java 11
+- **Intégrations optionnelles** : PlaceholderAPI (auto-détectée si installée)
 - **API serveur (provided)** : Paper 1.16.5
 - **SQLite (compile)** : `org.xerial:sqlite-jdbc:3.45.3.0`
 - **Package racine** : `fr.luc.crcore`