feat: add alt text extraction from URLs for images and improve CSS variable usage for progress bars

Add `_alt_from_url` helper in Python rendering and `altFromUrl` in JS ContentRenderer to generate descriptive alt attributes from image filenames, replacing empty alt strings. Update image embed templates and Avatar component to use derived alt text. Migrate inline `style.width` assignments to CSS custom properties (`--poll-pct`, `--hud-xp`, `--quest-pct`, `--bar-pct`, `--quota-pct`) across PollManager, GameFarm, and profile/quest CSS for better maintainability. Introduce new admin, docs, projects, services, and base CSS utility classes. Add "Code Farm" docs page entry.

devplacepy/static/js/components/AppLightbox.js

@@ -72,7 +72,7 @@ export class AppLightbox extends Component {
         const opts = options || {};
         if (!src) return;
         this.image.src = src;
-        this.image.alt = opts.alt || "";
+        this.image.alt = opts.alt || "Enlarged image";
         this.lastFocus = document.activeElement;
         this.bodyOverflow = document.body.style.overflow;
         document.body.style.overflow = "hidden";