feat: initial CR-Core library (team + player + command framework)

Pure Maven library for CR Minecraft game plugins, targeting Paper 1.16.5.

Common abstractions (fr.luc.crcore.common): Identifiable, Named, ScoreHolder,
AbstractEntity, Repository<T>.

Team domain (fr.luc.crcore.team): Team entity with name/tag/color/leader/
visibility (PUBLIC|PRIVATE)/members/scores/spawn point, TeamMember,
TeamRole/TeamColor/TeamVisibility enums, TeamRanking record, TeamService with
overridable hooks (factories, validations, lifecycle events), in-memory
repository, dedicated exception hierarchy.

Player domain (fr.luc.crcore.player): PlayerProfile with named scores per
player, PlayerProfileService with auto-creation, individual rankings,
exception hierarchy. Both Team and PlayerProfile implement ScoreHolder.

Command framework (fr.luc.crcore.command): Command interface,
AbstractCommand base, BaseCommand (CommandExecutor + TabCompleter), SubCommand,
CommandContext, CommandResult, ArgumentType<T> + ArgumentTypes catalogue
(STRING, INTEGER, DOUBLE, BOOLEAN, ONLINE_PLAYER, enumOf, choice).

Docs (docs/) is the single source of truth: README, setup, features,
decisions log, and 6 PlantUML diagrams (team class/sequence/activity/join,
player class, command class).

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

.idea/.gitignore

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+# Default ignored files
+/shelf/
+/workspace.xml
+# Editor-based HTTP Client requests
+/httpRequests/
+# Ignored default folder with query files
+/queries/
+# Datasource local storage ignored files
+/dataSources/
+/dataSources.local.xml