refactor: Move recursion planner to lib/algorithms; remove dead bst.js

The recursion-tree builders + recursionActions planner now live in
src/lib/algorithms/recursion.js (was app/recursion-tree/fib.jsx), alongside the
other action-log planners. Also deletes the unused legacy app/recursion-tree/bst.js.

Author: TamimEhsan

src/app/recursion-tree/bst.js

@@ -2,7 +2,7 @@
 
 import { useState } from 'react';
 import Navbar from '@/components/navbar';
-import { getTree, recursionActions } from './fib';
+import { getTree, recursionActions } from '@/lib/algorithms/recursion';
 import { buchheimLayout } from '@/components/tree/layout';
 import { useTreeEditor } from '@/components/tree/use-tree-editor';
 import TreeCanvas from '@/components/tree/tree-canvas';