fix: visual alignment and spacing issues

- Fix icon+text alignment in 'Continue as Guest' button (Login)
- Fix icon+text alignment in 'Sign In' button (Guest header)
- Standardize form section spacing in Calculator and GuestCalculator

Author: TheLastAirbenderAng

src/pages/Calculator.jsx

@@ -249,7 +249,7 @@ export default function Calculator() {
             </div>
 
             {/* Items Section */}
-            <div className="space-y-4">
+            <div className="space-y-3">
               <Label>Items you owe</Label>
               <div className="space-y-3">
                 {items.map((item, index) => (

src/pages/GuestCalculator.jsx

@@ -139,7 +139,7 @@ export default function GuestCalculator() {
             </Button>
 
             <Button variant="outline" size="sm" asChild>
-              <Link to="/login">
+              <Link to="/login" className="flex items-center">
                 <LogIn className="h-4 w-4 mr-2" />
                 Sign In
               </Link>
@@ -184,7 +184,7 @@ export default function GuestCalculator() {
             </div>
 
             {/* Items Section */}
-            <div className="space-y-4">
+            <div className="space-y-3">
               <Label>Items you owe</Label>
               <div className="space-y-3">
                 {items.map((item, index) => (

src/pages/Login.jsx

@@ -196,7 +196,7 @@ export default function Login() {
             className="w-full"
             asChild
           >
-            <Link to="/guest">
+            <Link to="/guest" className="flex items-center justify-center">
               <UserX className="h-4 w-4 mr-2" />
               Continue as Guest
             </Link>