fix(settings): keep Steam ID as string and store the new token

Number("76561198005679788") is 76561198005679790 in JavaScript, so the wrong
Steam ID was saved. The Steam ID now stays a 17-digit string. Theme and
language saves no longer send steamId 0. After a save the new token from Auth
replaces the old one.

Add Vitest and run it in CI.

src/utils/validation.js

@@ -15,14 +15,12 @@ const inviteCodeField = z
     .string()
     .min(1, 'VALIDATION.INVITE_CODE_REQUIRED');
 
-// Backend stores steamId as a primitive long; Steam IDs are positive 64-bit integers.
+// A SteamID64 has 17 digits. Keep it a string: a JS number loses precision above 2^53.
 const steamIdField = z
-    .union([z.string(), z.number()])
-    .transform((v) => (typeof v === 'string' ? v.trim() : String(v)))
-    .refine((v) => v.length > 0, {message: 'VALIDATION.STEAM_ID_REQUIRED'})
-    .refine((v) => /^\d+$/.test(v), {message: 'VALIDATION.STEAM_ID_INVALID'})
-    .transform((v) => Number(v))
-    .refine((n) => Number.isFinite(n) && n > 0, {message: 'VALIDATION.STEAM_ID_INVALID'});
+    .string()
+    .trim()
+    .min(1, 'VALIDATION.STEAM_ID_REQUIRED')
+    .regex(/^\d{17}$/, 'VALIDATION.STEAM_ID_INVALID');
 
 export const registrationSchema = z
     .object({

src/utils/validation.test.js

@@ -0,0 +1,30 @@
+import {describe, expect, it} from 'vitest';
+import {registrationSchema, settingsSchema} from './validation.js';
+
+const settings = (steamId) => ({useDarkTheme: true, language: 'de', steamId});
+
+describe('steamId validation', () => {
+    it('keeps a SteamID64 as the exact string', () => {
+        // Number('76561198005679788') is 76561198005679790
+        expect(settingsSchema.parse(settings('76561198005679788')).steamId).toBe('76561198005679788');
+    });
+
+    it('trims whitespace', () => {
+        expect(settingsSchema.parse(settings(' 76561198005679788 ')).steamId).toBe('76561198005679788');
+    });
+
+    it.each(['', '12345', '7656119800567978x', '765611980056797880'])('rejects %j', (steamId) => {
+        expect(settingsSchema.safeParse(settings(steamId)).success).toBe(false);
+    });
+
+    it('keeps the exact string on registration', () => {
+        const result = registrationSchema.parse({
+            email: 'a@b.de',
+            password: 'password1',
+            passwordConfirmation: 'password1',
+            inviteCode: 'code',
+            steamId: '76561198005679788',
+        });
+        expect(result.steamId).toBe('76561198005679788');
+    });
+});