Centralize dependencies: version catalog, pin Paper 1.21.11 everywhere, single mono-repo version

Monorepo-wide build hygiene (filed under Treasury as the core build; touches every JVM module).

Goals

1. Pin Paper API to 1.21.11 everywhere. business (main+test), business-api, and treasury-api-plugin were stuck on 1.21.10-R0.1-SNAPSHOT while treasury/chestshop are on 1.21.11. Also pin hibernia-framework to 1.0.2 everywhere (business-api was on 0.1.2).
2. Lift common dependency versions to a Gradle version catalog (gradle/libs.versions.toml) — one source of truth for the shared libs (paper, hibernia, lombok, guice, hikari, mariadb, mybatis, reflections, jjwt, luckperms, log4j, junit, assertj, mockito, mariaDB4j, flyway, jacoco). The core plugin modules reference libs.*; chestshop/rest-api adopt the shared subset.
3. Single version across the mono-repo. All JVM modules inherit 2.2.1-SNAPSHOT from the root allprojects block (was: treasury-api-plugin 2.1.0, treasury-rest-api 2.1.0, economy-flyway 1.0.0, chestshop 4.0.2). ChestShop is included per decision.

Notes

• JUnit drift (5.11.3 vs chestshop 5.13.3) standardised upward to 5.13.3 in the catalog.
• Keeps Java 21 bytecode target and Gradle 9.6 (PAR-241) unchanged.
• treasury-api-plugin plugin.yml version aligned to 2.2.1.

Acceptance

• One Paper version (1.21.11) and one framework version (1.0.2) across all modules.
• gradle/libs.versions.toml holds the shared versions; no duplicated version literals for them.
• Every module reports the same project version; ./gradlew build green (incl. the 95% coverage gates).