fix: [DEFECT] block-editor-renderer heading not applying correct level in @dotcms/angular (#34297)

[zJaaal]

Fixes #34297

Summary

• Fixed DotHeadingBlock to accept level as a number or string — the Block Editor serializes heading levels as numbers, causing the @switch to always fall through to @default and render <h1>.
• Added a normalizedLevel getter that coerces level to a string before the switch comparison.
• Replaced multiple <ng-content /> usages inside @switch branches with a single <ng-template #content> + *ngTemplateOutlet to fix Angular's "duplicated ng-content" content projection error.
• Added style input to DotHeadingBlock to accept style attributes from block editor node attrs.
• Added unit tests covering numeric level handling and heading content rendering.

Test plan

• Verify headings h1–h6 render with the correct tag when level is a number
• Verify heading content (text, marks) is projected correctly inside each heading level
• Run nx test sdk-angular — all new and existing tests should pass

🤖 Generated with Claude Code

This PR fixes: #34297