feat: Replace cookiecutter with built-in MiniJinja templating

- Add MiniJinja dependency for Jinja2-compatible templating
- Create new project_template.rs module for template rendering
- Bundle snowflake template in templates/snowflake/ directory
- Remove dependency on external cookiecutter Python tool
- Handle Gitea publishing natively in Rust instead of Python hooks
- Update default template path to use bundled template with fallback
- Update README to reflect new built-in templating
- All tests pass

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

README.md

@@ -486,12 +486,16 @@ title page, if you asked for one) and one linked section per chapter; LibreOffic
 treat it as a starting point to relink rather than as the assembled book. For a
 single finished document, use **Export ODT**.
 
-## New projects from a cookiecutter template
+## New projects from templates
 
 **File ▸ ✨ New project…** scaffolds a whole manuscript project from a
-[cookiecutter](https://cookiecutter.readthedocs.io/) template and then opens its
-drafting folder as the workspace, so you go from nothing to editing chapters in
-one step.
+template and then opens its drafting folder as the workspace, so you go from
+nothing to editing chapters in one step.
+
+The app now uses **built-in MiniJinja templating** (no external Python
+cookiecutter required) to render templates. A default "snowflake" template is
+bundled in the `templates/snowflake/` folder of the project, which you can modify
+by hand to customise the project structure or file contents.
 
 The dialog asks for a **name**, **author**, **description** and the **folder to
 create it in** (prefilled with wherever you put the last one). Those are passed
@@ -510,27 +514,34 @@ A folder only appears in the file panel once it holds a `.md` file — the
 template's empty acts are held open with `.gitkeep`, which is not markdown, so
 they show up as you add scenes to them.
 
+You can use your own templates by pointing the **Template** setting in
+**Settings ▸ New project…** at any folder containing a `cookiecutter.json` file.
+The template should contain a subdirectory named with a template expression
+(e.g., `{{ cookiecutter.project_name }}`) which becomes the project root after
+rendering.
+
 ### Settings ▸ New project…
 
 | Setting | Meaning |
 |---|---|
-| **Template** | the folder holding the template's `cookiecutter.json`. Defaults to `~/Documents/Cookiecutters/snowflake`; the dialog confirms whether a `cookiecutter.json` is actually there |
+| **Template** | the folder holding the template's `cookiecutter.json`. Defaults to the bundled `templates/snowflake`; falls back to `~/Documents/Cookiecutters/snowflake` |
 | **Open subfolder** | which folder of the generated project becomes the workspace (default `06-First Draft`; blank opens the project root) |
-| **cookiecutter path** | leave blank to search `PATH` and then the usual per-user Python prefixes (`~/.anaconda3/bin`, `~/miniconda3/bin`, `~/.local/bin`, …), which is what a desktop launcher needs since it does not inherit a conda `PATH`. The dialog shows which executable was found |
-| **Run the template's hooks** | whether to run the template's pre/post-generation scripts (on by default) |
-| **Gitea** | server URL, user and token, handed to the hooks as `GITEA_URL` / `GITEA_USER` / `GITEA_TOKEN` |
+| **Publish to Gitea after creation** | when enabled and Gitea credentials are configured below, a new repository will be created and the project pushed to it |
+| **Gitea** | server URL, user and token, used to create repositories when publishing is enabled |
 
-Cookiecutter is a Python program and is **not bundled** — install it with
-`pip install cookiecutter` or `conda install cookiecutter` if the settings window
-reports it missing.
+No external tools are required — templating is built into the application.
 
-### Hooks and publishing
+### Publishing to Gitea
 
-The snowflake template's `hooks/post_gen_project.py` creates a repository on a
-Gitea server and pushes the new project to it. It only does that when all three
-Gitea settings are filled in; with any of them blank it prints a note and skips,
-and **the project is still generated either way**. The token is passed to the
-push command alone and is not written into the project's `.git/config`.
+When **Publish to Gitea after creation** is enabled and all three Gitea settings
+(**Server URL**, **User**, **Token**) are filled in, the app will:
+1. Initialize a git repository in the new project
+2. Create a repository on the Gitea server
+3. Set the `origin` remote to point at the new repository
+
+The token is passed to the push command temporarily and is not written into the
+project's `.git/config`. With any setting blank, publishing is skipped but
+the project is still generated locally.
 
 The token is stored in `config.json` in plain text, the same as the Mistral API
 key.