v3: code quality pass, various bug fixes

src/config/api.ts

@@ -8,3 +8,20 @@ const serverPort = import.meta.env.VITE_SERVER_PORT || "8000";
 
 export const API_URL = `${apiProtocol}://${serverHost}:${serverPort}`;
 export const WS_URL = API_URL.replace(/^http/, "ws");
+
+export const DEFAULT_PAGE_SIZE = 20;
+export const NOTIFICATIONS_PAGE_SIZE = 30;
+
+// Validation constants (mirrors api/model/interfaces.ts VALIDATION)
+export const VALIDATION = {
+  USERNAME_MIN: 1,
+  USERNAME_MAX: 32,
+  PASSWORD_MIN: 8,
+  PASSWORD_MAX: 128,
+  DUMP_TITLE_MAX: 200,
+  DUMP_COMMENT_MAX: 5000,
+  PLAYLIST_TITLE_MAX: 100,
+  PLAYLIST_DESCRIPTION_MAX: 2000,
+  COMMENT_BODY_MAX: 5000,
+  USER_DESCRIPTION_MAX: 2000,
+} as const;