feat: centralize PHP lint workflows

[vitormattos]

Summary

Continue #15 by centralizing the PHP lint workflows as reusable workflows with thin organization-template callers.

This PR adds reusable implementations for:

• lint-php;
• lint-php-cs.

The corresponding catalog templates keep only the repository-owned pull_request trigger and call the reusable implementations pinned to immutable commit bc97b54e3d33d58d6075a0994883acde00f0556c.

Improvements over current consumer copies

• update actions/checkout to v7.0.1;
• use nextcloud-libraries/nextcloud-version-matrix v1.3.3;
• use shivammathur/setup-php 2.37.2;
• keep all third-party actions pinned to full SHAs;
• use public ubuntu-latest instead of Nextcloud-specific low-cost runners;
• centralize the PHP lint matrix and coding-standards implementation;
• avoid direct template interpolation inside shell for the summary result.

Distribution model

Consumers retain only small event callers. Future implementation changes remain explicit because callers are pinned and updated through the catalog/consumer synchronization path.

After this merges, LibreCodeCoop/extract can migrate both copied workflows to the thin callers.