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/templates/game.html

@@ -19,7 +19,7 @@
         <div class="hud-stat">
             <span class="hud-label">Level</span>
             <span class="hud-value" data-hud-level>{{ farm.level }}</span>
-            <div class="hud-xp-bar"><span class="hud-xp-fill" data-hud-xp-fill style="width: {% if farm.level_span %}{{ (100 * farm.level_into / farm.level_span)|round(0, 'floor') }}{% else %}100{% endif %}%"></span></div>
+            <div class="hud-xp-bar"><span class="hud-xp-fill" data-hud-xp-fill style="--hud-xp: {% if farm.level_span %}{{ (100 * farm.level_into / farm.level_span)|round(0, 'floor') }}{% else %}100{% endif %}%"></span></div>
             <span class="hud-sub" data-hud-xp>{% if farm.level_is_max %}max level{% else %}{{ farm.level_into }} / {{ farm.level_span }} XP{% endif %}</span>
         </div>
         <div class="hud-stat">