fix: preserve folder structure when pushing files

[admirkadriu]

Summary

olcli push currently uploads all files to the project root folder, ignoring subdirectory structure. For example, a file at figures/image.png or sections/intro.tex ends up at the root level on Overleaf instead of in its respective subfolder.

Root cause: uploadFile() in client.ts strips the directory portion of the file path (fileName.split('/').pop()) and always uploads to the root folder ID.

Fix:

• Added getFolderTreeFromSocket() to fetch the full folder hierarchy (path -> folder ID map) via the Socket.IO joinProjectResponse packet
• Added resolveFolderId() to look up or create missing folders on demand
• Modified uploadFile() to accept an optional folderTree parameter; when a file has a directory component, it resolves the correct subfolder ID instead of always using root
• Updated push command to fetch the folder tree once before uploading and pass it to each uploadFile() call

Behavior:

• Files at root level (e.g. main.tex) continue to upload to root as before
• Files in subdirectories (e.g. figures/img.png) are now uploaded into the correct subfolder
• If a subfolder doesn't exist on Overleaf, it is created automatically
• The folder tree is fetched once per push (not per file), so there is no performance penalty
• Backward compatible: callers that don't pass folderTree get the existing behavior

Test plan

• Tested with a real Overleaf project containing figures/ and sections/ subdirectories
• Verified files land in correct subfolders (not flattened to root)
• Verified new folders are created when they don't exist on Overleaf
• Verified root-level files still upload correctly
• TypeScript compiles cleanly (npm run build)

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