feat(config): add item list selector

[anolithme]

Summary

• add a reusable @ItemList config option backed by namespaced item IDs
• support searchable single and multiple item selection, entry limits, removal, and drag reordering
• render registered Minecraft item previews through a version-aware catalog service with bounded caching
• add documentation, translations, a test configuration, and focused unit coverage

API

@ItemList(
    title = "Tracked items",
    description = "Items shown by the tracker",
    maxEntries = 8
)
public List<String> trackedItems = new ArrayList<>(List.of(
    "minecraft:diamond",
    "minecraft:golden_apple"
));

String[] and List<String> are supported. Setting maxEntries = 1 provides a single-item selector. Unknown registry IDs are preserved so temporarily missing modded items are not silently removed.

Testing

• ./gradlew :modules:config-impl:j21Tests
• ./gradlew :modules:internal:j21Tests
• ./gradlew :modules:config-impl:apiCheck
• classes for Minecraft 1.21.1, 1.21.4, 1.21.5, 1.21.8, 1.21.10, and 1.21.11
• compileKotlin for Minecraft 26.1 and 26.2
• manual verification on Fabric 1.21.11

Environment note

The full local 26.1 classes task requires a Java 25 toolchain because its ModMenu shim targets Java 25. The changed Kotlin source compiled successfully for both 26.1 and 26.2.

Closes #443