Mirrors the old site's Bildergalerie structure: a brand tile grid at
/galerie, project tiles within a brand, and a photo grid with a
lightbox for each project. Backed by new gallery_brands/gallery_projects/
gallery_photos tables and admin CRUD pages, gated by a new gallery.manage
permission.
Also fixes a real bug found while testing photo uploads: Apache's
mod_dir was redirecting POST /api/uploads to /api/uploads/ (a trailing
slash) because api/uploads/ exists as a real directory, silently
dropping the multipart body on every image upload across the whole
app. Fixed via DirectorySlash Off in .htaccess.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
