fix: LIGHT variant bg animations, decoration grid spacing, bug doc updates

- chatBackground.ts: remove animRainGlowKeyframe and animGridBrightnessKeyframe
  from LIGHT anim-rain and anim-pulse definitions (these were removed from the
  import and from DARK variants in the previous session but the LIGHT variants
  were missed, leaving stale references that would cause a build error)
- ProfileDecoration.tsx: increase decoration grid gap 20→36 (visual gap was
  only 4px due to 8px image overflow beyond each 52×52 button), fix paddingBottom
  4→8 and add paddingRight:8 to prevent edge clipping
- LOTUS_BUGS.md: correct bug #8 root cause (CSP, not lazy-loading), add
  bugs #9 (grid spacing) and #10 (Windows taskbar badge)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/features/lotus/chatBackground.ts

@@ -428,7 +428,7 @@ const LIGHT: Record<ChatBackground, CSSProperties> = {
     ].join(','),
     backgroundSize: '40px 200px, 12px 200px',
     backgroundPosition: '0 0, 0 0',
-    animation: `${animRainKeyframe} 8s linear infinite, ${animRainGlowKeyframe} 2.1s ease-in-out infinite`,
+    animation: `${animRainKeyframe} 8s linear infinite`,
   },
 
   'anim-stars': {
@@ -452,7 +452,7 @@ const LIGHT: Record<ChatBackground, CSSProperties> = {
       'linear-gradient(90deg, rgba(0,98,184,0.06) 1px, transparent 1px)',
     ].join(','),
     backgroundSize: '60px 60px, 60px 60px, 12px 12px, 12px 12px',
-    animation: `${animGridPulseKeyframe} 4s ease-in-out infinite, ${animGridBrightnessKeyframe} 3.3s ease-in-out infinite`,
+    animation: `${animGridPulseKeyframe} 4s ease-in-out infinite`,
   },
 
   'anim-aurora': {