✨♻️💄 app, frontend, README: Update content, theme handling, and styles

- Added `Codeberg` link to contact page in `contact.rs`
- Removed `Auto` theme option and set `Dark` as default in `theme_switcher`
- Updated biography text and link formatting in `HomePage` component
- Simplified theme CSS structure and adjusted color variables in `styles.css`
- Removed outdated SHA256 warning and added `Cargo.toml` note in `README.md`

README.md

@@ -4,8 +4,6 @@ My personal website. Hosted at [mascully.com](https://mascully.com). The current
 
 Built using [Leptos](https://leptos.dev/) with [Axum](https://github.com/tokio-rs/axum).
 
-This repo uses the SHA256 object format so it may be incompatible with a lot of tools. See [here](https://github.com/NixOS/nix/issues/11561) for instructions on using this repo with Nix.
-
 ## Running
 
 ### Nix
@@ -40,6 +38,7 @@ The bind address and port can be modifed in the top-level `Cargo.toml` file unde
 - `crates/frontend`: Images, fonts, CSS.
 - `crates/server`: A minimal Axum server for serving pages.
 - `flake.nix`: This doesn't work; ignore it.
+- `Cargo.toml`: Includes metadata for configuring Leptos.
 
 ## License