Add "Note templates" for quick setup

## 📌 Summary
To improve the user experience and make note creation faster, this contribution proposes **adding pre-defined Markdown templates** that users can use as a starting point when creating new notes in ZettaNote.

These templates will serve as ready-to-use note structures, helping users avoid starting from a blank page every time.

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## 📁 What This Contribution Includes
- A set of **pre-made Markdown note templates** (e.g., Meeting Notes, Study Notes, Project Plan).
- All templates will be stored in a dedicated `templates/` folder inside the repository.
- Each template will be a standalone `.md` file for easy access and future integration.

## ✅ Benefits

- Provides users with a quick starting point for common note types.
- Ensures consistency and structure across similar notes.
- Prepares the project for future features like a **"Use Template"** button.

Create the dedicated templates/ folder and review the repository structure before adding the proposed standalone Markdown files. Define templates such as Meeting Notes, Study Notes, and Project Plan, then confirm that each file provides a ready-to-use note structure and is easy to access for future integration.

Written by the indexing model from the issue text.