Align phpdoc-bootstrap-template visuals with Fast Forward .github/profile brand identity

[coisa]

Context

phpdoc-bootstrap-template uses a functional Bootstrap layout, but the visual style has drifted from the Fast Forward brand presentation now used in .github/profile assets.

This issue asks to adapt the existing template, preserving current structure and behavior, so rendered documentation keeps the same template logic while following the current visual identity.

Reference

Current style target (already used by the Fast Forward .github/profile README mockups):

Problem

• Documentation output is technically stable, but it does not reflect the latest brand identity.
• We need tighter visual alignment (colors, spacing scale, hierarchy, callout/section styling, and overall page rhythm) while keeping the template’s current capabilities.

Goal

• Keep the existing phpDocumentor Bootstrap base and inheritance model.
• Refine visual tokens and layout styling to match the brand reference.
• Keep compatibility with current public usage, including template entrypoint and generation flow.

Non-Goals

• No migration to a different template engine.
• No functional change in phpDocumentor generation.
• No new major JS behavior unless needed only for style support.

Proposed implementation

1. Review current main template entry points and styling layers (e.g. template.xml, base.html.twig, shared partials, stylesheet hooks).
2. Update existing style overrides to approximate the reference:
   • color palette and contrast;
   • typography rhythm and heading scale;
   • spacing/padding consistency;
   • cards, nav, and table/section treatment.
3. Keep all existing semantic structure intact.
4. Validate rendering with the default guide output and a minimal PHP project.

Acceptance criteria

• Rendered docs with current template logic maintain existing behavior.
• Style is visibly aligned to the reference image and FF brand guide cues.
• No breaking changes for existing consumers.
• At least one manual review screenshot (or equivalent visual diff check) confirms improved visual parity.
• No unrelated scope changes beyond template styling and visual identity alignment.

Definition of done

• Files updated under the existing template layers only.
• README (if needed) updated with any relevant note on visual customization.
• CI/tests or checks for the repository (if applicable) pass.