feat: add Google sign-in button to WinScreen and footer provider label

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

src/lib/components/WinScreen.svelte

@@ -357,6 +357,26 @@
 					Sign in with Apple
 				</button>
 			</form>
+			<form method="POST" action="/auth/google" class="w-full">
+				<input type="hidden" name="anonymousId" value={anonymousId} />
+				<button
+					type="submit"
+					class="google-signin-btn"
+					data-umami-event="Sign in with Google"
+				>
+					<svg
+						class="google-icon"
+						viewBox="0 0 24 24"
+						xmlns="http://www.w3.org/2000/svg"
+					>
+						<path fill="#4285F4" d="M22.56 12.25c0-.78-.07-1.53-.2-2.25H12v4.26h5.92c-.26 1.37-1.04 2.53-2.21 3.31v2.77h3.57c2.08-1.92 3.28-4.74 3.28-8.09z"/>
+						<path fill="#34A853" d="M12 23c2.97 0 5.46-.98 7.28-2.66l-3.57-2.77c-.98.66-2.23 1.06-3.71 1.06-2.86 0-5.29-1.93-6.16-4.53H2.18v2.84C3.99 20.53 7.7 23 12 23z"/>
+						<path fill="#FBBC05" d="M5.84 14.09c-.22-.66-.35-1.36-.35-2.09s.13-1.43.35-2.09V7.07H2.18C1.43 8.55 1 10.22 1 12s.43 3.45 1.18 4.93l3.66-2.84z"/>
+						<path fill="#EA4335" d="M12 5.38c1.62 0 3.06.56 4.21 1.64l3.15-3.15C17.45 2.09 14.97 1 12 1 7.7 1 3.99 3.47 2.18 7.07l3.66 2.84c.87-2.6 3.3-4.53 6.16-4.53z"/>
+					</svg>
+					Sign in with Google
+				</button>
+			</form>
 		</div>
 	{/if}
 </div>
@@ -710,6 +730,57 @@
 		flex-shrink: 0;
 	}
 
+	.google-signin-btn {
+		display: flex;
+		align-items: center;
+		justify-content: center;
+		gap: 0.5rem;
+		padding: 0.6rem 1rem;
+		width: 100%;
+		background: #fff;
+		color: #000;
+		border-radius: 0.5rem;
+		font-size: 0.95rem;
+		font-weight: 600;
+		border: 1px solid #dadce0;
+		cursor: pointer;
+		transition:
+			background 150ms ease,
+			border-color 150ms ease,
+			transform 80ms ease;
+	}
+
+	.google-signin-btn:hover {
+		background: #f8f8f8;
+		border-color: #bbb;
+		transform: translateY(-1px);
+	}
+
+	.google-signin-btn:active {
+		background: #f0f0f0;
+		transform: scale(0.98);
+	}
+
+	@media (prefers-color-scheme: dark) {
+		.google-signin-btn {
+			background: #1e1e1e;
+			color: #fff;
+			border: 1px solid #444;
+		}
+		.google-signin-btn:hover {
+			background: #2a2a2a;
+		}
+		.google-signin-btn:active {
+			background: #333;
+		}
+	}
+
+	.google-icon {
+		width: 1.1rem;
+		height: 1.1rem;
+		flex-shrink: 0;
+	}
+
 	.progress-btn {
 		display: flex;
 		align-items: center;

src/routes/+page.svelte

@@ -528,7 +528,7 @@
 					.filter(Boolean)
 					.join(" ")}{user.email
 					? ` (${user.email})`
-					: ""}{user.appleId ? " using Apple" : ""} |
+					: ""}{user.appleId ? " using Apple" : user.googleId ? " using Google" : ""} |
 
 				<form
 					method="POST"