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>

pom.xml

@@ -37,6 +37,10 @@
             <id>sonatype</id>
             <url>https://oss.sonatype.org/content/groups/public/</url>
         </repository>
+        <repository>
+            <id>placeholderapi</id>
+            <url>https://repo.extendedclip.com/content/repositories/placeholderapi/</url>
+        </repository>
     </repositories>
 
     <dependencies>
@@ -58,6 +62,18 @@
             <version>${sqlite.version}</version>
             <scope>compile</scope>
         </dependency>
+        <!--
+            PlaceholderAPI — intégration OPTIONNELLE. Scope provided : si PAPI
+            est installé sur le serveur, on enregistre nos placeholders ; sinon,
+            la hook reste dormante. Le plugin de jeu n'a pas besoin de l'ajouter
+            lui-même.
+        -->
+        <dependency>
+            <groupId>me.clip</groupId>
+            <artifactId>placeholderapi</artifactId>
+            <version>2.11.6</version>
+            <scope>provided</scope>
+        </dependency>
     </dependencies>
 
     <!--