GUI Builder generates getClass().getResource() for icons, which fails in modular/multi-module projects

### Apache NetBeans version

Apache NetBeans 27

### What happened

When using the NetBeans GUI Builder (Matisse) to set an icon for a component (e.g., JMenuItem), the generated code uses:

new ImageIcon(getClass().getResource("/path/to/icon.png"))

This works in simple monolithic applications, but **fails in modular projects (JPMS) or multi-module Maven/Gradle projects** where the icon resource resides in a different module.

The issue is that `getClass().getResource()` performs a **class-relative resource lookup**, which is subject to module encapsulation rules. If the resource is in another module (even if on the classpath), it returns `null`, causing a `NullPointerException` at runtime.

In contrast, `ClassLoader.getResource()` performs a **classpath-root lookup** and can access resources across module boundaries (if the class loader has visibility), making it more suitable for multi-module environments.

For example, this works:
new ImageIcon(getClass().getClassLoader().getResource("alwaystech/alwaysswing/resources/images/misc_preferences.png"))

Note:
- No leading `/` when using `ClassLoader.getResource()`
- The path is relative to the classpath root

Suggested Improvement:

Please modify the GUI Builder code generator to:
1. Detect if the project is modular or multi-module, OR
2. Provide an option in the IDE settings to prefer `ClassLoader.getResource()` over `getClass().getResource()`
3. Generate code using `getClassLoader().getResource(path)` (without leading `/`) when appropriate

Alternatively, allow users to define a custom resource loading strategy for icons in GUI forms.

This change would improve compatibility with modern Java project structures and avoid runtime resource loading failures.

Steps to Reproduce:
1. Create a multi-module Maven/Gradle project
2. Place an icon (e.g., misc_preferences.png) in resources of module A
3. In module B, use GUI Builder to set the icon for a JMenuItem
4. Run the application → Icon fails to load (NPE or blank)

### Language / Project Type / NetBeans Component

_No response_

### How to reproduce

1. Create a multi-module Maven/Gradle project
2. Place an icon (e.g., misc_preferences.png) in resources of module A
3. In module B, use GUI Builder to set the icon for a JMenuItem
4. Run the application → Icon fails to load (NPE or blank)

### Did this work correctly in an earlier version?

No / Don't know

### Operating System

debian12.5

### JDK

jdk25

### Apache NetBeans packaging

Apache NetBeans binary zip

### Anything else

_No response_

### Are you willing to submit a pull request?

No

Start with the NetBeans GUI Builder (Matisse) code generator and reproduce the icon-loading failure in a multi-module Maven or Gradle project. Compare generated getClass().getResource() usage with the requested ClassLoader.getResource() behavior, then verify the generated form runs successfully when the icon is in another module.

Written by the indexing model from the issue text.