Fix styling issues: dialog backgrounds, spacing tokens, and module category

- Added category 'Audio/Video' to module.json to fix 'Non répertorié' issue
- Created styles/tokens/_spacing.less with spacing tokens (xxs, xs, sm, md, lg, xl, 2xl)
- Added legacy aliases (--sp-space-xs, --sp-space-sm, --sp-space-m, etc.) for preset-import-export.less
- Added --sp-bg and --sp-surface-elevated tokens to _base.less
- Fixed _player-privacy-panel.less to use CSS custom properties instead of LESS variables
- Added background: var(--sp-surface) to all dialog root elements:
  - PlayerPrivacyPanel
  - PresetSaveDialog
  - PresetLoadDialog
  - DirectorsBoard
  - PresetImport/Export dialogs
- Added _spacing.less import to scrying-pool.less
- Rebuilt CSS (dist/styles/scrying-pool.css)

This fixes:
1. Transparent dialogs (now have proper background colors)
2. Missing spacing tokens (caused build errors)
3. Module category (now shows as 'Audio/Video' instead of 'Uncategorized')

All 900 unit tests passing.

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

module.json

@@ -8,6 +8,7 @@
       "name": "Morr"
     }
   ],
+  "category": "Audio/Video",
   "compatibility": {
     "minimum": "14",
     "verified": "14"