feat: add chat page layout with message list and bubble components

- Create /chat route with scrollable message list
- MessageBubble component with distinct user/assistant styles
- MessageList with auto-scroll-to-bottom on new messages
- Empty state display when no messages
- ChatMessage type definition in src/lib/types.ts
- Add browser globals to ESLint config for Svelte files

Closes #5

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

eslint.config.js

@@ -2,6 +2,7 @@ import js from '@eslint/js';
 import svelte from 'eslint-plugin-svelte';
 import prettier from 'eslint-config-prettier';
 import ts from 'typescript-eslint';
+import globals from 'globals';
 
 export default ts.config(
 	js.configs.recommended,
@@ -12,6 +13,9 @@ export default ts.config(
 	{
 		files: ['**/*.svelte', '**/*.svelte.ts', '**/*.svelte.js'],
 		languageOptions: {
+			globals: {
+				...globals.browser
+			},
 			parserOptions: {
 				parser: ts.parser
 			}