feat: replace gunicorn entrypoint with python -m snek.app and add MIT license, pyproject.toml metadata, form/model refactor, and new view structure

Replace the Dockerfile CMD from gunicorn to `python -m snek.app`, add MIT LICENSE.txt, populate pyproject.toml with project metadata and dependencies, refactor forms into `snek.form.login` and `snek.form.register` with new HTMLElement system, delete old `snek/forms.py`, add `snek/model/user.py` with User model, restructure `snek/app.py` imports and router setup to use new view modules, rename `styles.css` to `base.css` and strip comments, add `fancy-button.js` custom element, and update `compose.yml` entrypoint accordingly.

LICENSE.txt

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2025 retoor
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.