fix(addon): prevent add-on names from colliding with application name

[lmmendes]

Description

An add-on could be created with exactly the same name as its application. The add-on form checked startsWith(appName), so an exact match was incorrectly treated as already prefixed. Although the application and add-on are different Kubernetes resource kinds, the Helm operator uses their names as release names within the same namespace. This caused reconciliation to fail with a duplicate release name error.

This change:

• treats an add-on name as prefixed only when it starts with <app-name>-;
• preserves the prefix correctly when editing an existing add-on;
• validates Kubero-managed add-on release names on both application creation and update;
• rejects names that collide with the application or another Kubero add-on;
• adds unit tests for colliding, duplicate, and valid prefixed names;
• validates app-name validation in both the UI and the backend so the name is a valid Kubernetes DNS-1123 label (lowercase letters/numbers/hyphens, no spaces, no underscores, and must start/end with a letter or number).

Type of change

• Template (non-breaking change which adds a template)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

• Server production build passed;
• Client type-check and production build passed;
• Full server test suite passed: 57 suites and 541 tests;
• A Kind test reproduced the original collision using KuberoApp/demo and KuberoAddonPostgres/demo;
• The add-on was recreated with the normalized name demo-postgres. Both KuberoApp/demo and KuberoAddonPostgres/demo-postgres reached Deployed=True, with separate deployed Helm releases and no duplicate release name errors;
• I've built the image and tested it on a kubernetes cluster - note: using kind

Test Configuration:

• Operator Version: v0.2.2
• Kubernetes Version: v1.35.0 (Kind with Podman, arm64)
• Kubero CLI Version (if applicable):

Checklist:

• I removed unnecessary debug logs
• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I documented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes