Display the app version dynamically

[baimard]

What changed

• reads the installed Gestion version through Nextcloud's IAppManager
• exposes that version to every page through the shared template parameters
• replaces the two hard-coded changelog versions with the dynamic value
• displays Gestion version … at the bottom of the navigation menu
• reduces the VAT exemption-reason action to a 30 × 30 px button with a 20 px icon

Translation catalogs remain untouched because they are managed through Transifex.

Why

appinfo/info.xml should be the single source of truth for the application version. Changing its <version> value now updates the changelog and navigation automatically at runtime.

The smaller VAT exemption action keeps the product actions column compact.

Validation

• PHP syntax checks
• Nextcloud dependency-injection container resolves TemplateService
• runtime app version matches appinfo/info.xml (3.2.10)
• webpack production build
• template script verification
• no hard-coded 3.2.8 remains in the changelog
• no l10n/ or Transifex files changed