chore(frontend): remove scaffold comments and add conventions doc

frontend/src/app.d.ts

@@ -1,17 +1,11 @@
-// See https://svelte.dev/docs/kit/types#app.d.ts
-// for information about these interfaces
 import type { SessionUser } from '$lib/types';
 
 declare global {
 	namespace App {
-		// interface Error {}
 		interface Locals {
 			user: SessionUser | null;
 			accessToken: string | null;
 		}
-		// interface PageData {}
-		// interface PageState {}
-		// interface Platform {}
 	}
 }
 

frontend/src/app.html

@@ -3,7 +3,6 @@
 	<head>
 		<meta charset="utf-8" />
 		<meta name="viewport" content="width=device-width, initial-scale=1" />
-		<meta name="text-scale" content="scale" />
 		%sveltekit.head%
 	</head>
 	<body data-sveltekit-preload-data="hover">

frontend/src/lib/index.ts

@@ -1 +0,0 @@
-// place files you want to import through the `$lib` alias in this folder.