feat: support item model keys and namespaced materials for blueprint bundle icon

[tastybento]

Summary

Resolves #2940

The "icon" field in blueprint bundle JSON files now accepts three formats without any change to existing configs:

• Plain material name (existing): "icon": "DIAMOND"
• Vanilla namespaced material (new): "icon": "minecraft:diamond"
• Custom item model key (new): "icon": "myserver:island_tropical"

How it works

Material.matchMaterial() is tried first — this handles both plain names and vanilla namespaced keys. If the string contains a : and is not a recognised vanilla material, it is treated as a custom item model key applied to a PAPER base item via ItemMeta.setItemModel(NamespacedKey).

Backward compatibility

• getIcon() (returns Material) is unchanged in signature — existing addons that call this continue to work, receiving PAPER for custom model keys.
• New getIconItemStack() method returns the full ItemStack with model data applied.
• setIcon(Material) overload preserved; new setIcon(String) overload added.
• Panels (BlueprintManagementPanel, IslandCreationPanel) updated to call getIconItemStack() so custom model icons actually render.

Test plan

• New BlueprintBundleTest covers: plain name, minecraft: namespaced, custom model key, null/fallback cases
• Existing BlueprintManagementPanelTest and IslandCreationPanelTest updated with getIconItemStack() stubs
• All three test classes pass

🤖 Generated with Claude Code

[tastybento]

Example blueprint bundle JSON:

{
  "uniqueId": "test",
  "icon": "bentobox:island_star",
  "displayName": "test",
  "description": [
    "Okay here's a description <blue>blue!</blue>"
  ],
  "requirePermission": false,
  "blueprints": {
    "NORMAL": "island"
  },
  "slot": 9,
  "times": 0,
  "cost": 7.0,
  "commands": []
}

Also works just by clicking on the icon in the blueprint admin GUI to set the icon.

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
80.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud