feat(ui): enhance timeline sidebar with slide-in animation and responsive layout

- Add slide-in animation to timeline sidebar using framer-motion
- Implement responsive layout adjustments for main content area
- Add proper timeline header with close button
- Fix floating prompt input positioning to accommodate timeline
- Reorder CSS imports for proper style precedence
- Fix animation scaling issue in rotating symbol keyframes

The timeline now slides in from the right with a smooth spring animation
and properly adjusts the main content area width on larger screens.

src/styles.css

@@ -423,9 +423,9 @@ button:focus-visible,
 /* Rotating symbol animation */
 @keyframes rotate-symbol {
   0%   { content: "◐"; transform: scale(1); }
-  25%  { content: "◓"; transform: scale(10); }
+  25%  { content: "◓"; transform: scale(1); }
   50%  { content: "◑"; transform: scale(1); }
-  75%  { content: "◒"; transform: scale(10); }
+  75%  { content: "◒"; transform: scale(1); }
   100% { content: "◐"; transform: scale(1); }
 }