fix: add file: prefix to org-mode links for Emacs resolution

Emorg org-mode requires [[file:path]] syntax for file links to be
clickable. Updated both extract.mjs and scaffold-notes.mjs generators,
and fixed all 200 existing note files.

leetcode/scaffold-notes.mjs

@@ -41,7 +41,7 @@ for (const line of roadmap.split("\n")) {
     const content = `* TODO ${num}. ${name} :${diff}:
 #+PROPERTY: STUDY_DECK_02
 :PROPERTIES:
-:NEETCODE: [[${relPath}][Roadmap]]
+:NEETCODE: [[file:${relPath}][Roadmap]]
 :END:
 
 ** TODO Approach