normalize project structure: src/client + src/server + src/shared, standardize biome to lineWidth 80

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

.vscode/tasks.json

@@ -5,13 +5,10 @@
 			"label": "vite: dev server",
 			"type": "shell",
 			"command": "npm",
-			"args": [
-				"run",
-				"dev"
-			],
+			"args": ["run", "dev"],
 			"isBackground": true,
 			"problemMatcher": [],
 			"group": "build"
 		}
 	]
-}
+}