Add frontend autoformatting and set CI to require formatted code for all languages (#6052)

# Description of Changes
Changes the strategy for autoformatting to reject PRs if they are not
formatted correctly instead of allowing them to merge and then spawning
a new PR to fix the formatting. The old strategy just caused more work
for us because we'd have to manually approve the followup PR and get it
merged, which required 2 reviewers so in practice it rarely got done and
just meant everyone's PRs ended up containing reformatting for unrelated
files, which makes code review unnecessarily difficult. If the PR's code
is not formatted correctly after this PR, a comment will be added
automatically to tell the author how to run the formatter script to fix
their code so it can go in.

This also enables autoformatting for the frontend code, using Prettier.
I've enabled it for pretty much everything in the frontend folder, other
than 3rd party files and files it doesn't make sense for. I also
excluded Markdown because it sounds likely to be more annoying to have
to autoformat the Markdown in the frontend folder but nowhere else. Open
to changing this though if people disagree.

> [!note]
> 
> Advice to reviewers: The first commit contains all of the actual logic
I've introduced (CI changes, Prettier config, etc.)
> The second commit is just the reformatting of the entire frontend
folder.
> The first commit needs proper review, the second one just give it a
spot-check that it's doing what you'd expect.

frontend/src/saas/components/auth/GuestUserBanner.tsx

@@ -1,88 +1,82 @@
-import React, { useEffect, useState } from 'react'
-import { useTranslation } from 'react-i18next'
-import CloseIcon from '@mui/icons-material/Close'
-import PersonAddIcon from '@mui/icons-material/PersonAdd'
-import { useAuth } from '@app/auth/UseSession'
-import { isUserAnonymous } from '@app/auth/supabase'
-import { withBasePath } from '@app/constants/app'
-import '@app/components/auth/GuestUserBanner.css'
+import React, { useEffect, useState } from "react";
+import { useTranslation } from "react-i18next";
+import CloseIcon from "@mui/icons-material/Close";
+import PersonAddIcon from "@mui/icons-material/PersonAdd";
+import { useAuth } from "@app/auth/UseSession";
+import { isUserAnonymous } from "@app/auth/supabase";
+import { withBasePath } from "@app/constants/app";
+import "@app/components/auth/GuestUserBanner.css";
 
 interface GuestUserBannerProps {
-  className?: string
+  className?: string;
 }
 
 // Ensure the toast only appears once per full page load, not on re-hydration
-let hasShownThisLoad = false
+let hasShownThisLoad = false;
 
 /**
  * Guest user toast encouraging account creation.
  * Appears 2s after load, top-right of the viewport, offset by right rail.
  */
-export function GuestUserBanner({ className = '' }: GuestUserBannerProps) {
-  const { t } = useTranslation()
-  const { session } = useAuth()
-  const [isDismissed, setIsDismissed] = useState(false)
-  const [visible, setVisible] = useState(false)
+export function GuestUserBanner({ className = "" }: GuestUserBannerProps) {
+  const { t } = useTranslation();
+  const { session } = useAuth();
+  const [isDismissed, setIsDismissed] = useState(false);
+  const [visible, setVisible] = useState(false);
 
-  const isAnon = Boolean(session?.user && isUserAnonymous(session.user))
+  const isAnon = Boolean(session?.user && isUserAnonymous(session.user));
 
   useEffect(() => {
-    if (!isAnon || hasShownThisLoad) return
+    if (!isAnon || hasShownThisLoad) return;
 
     const timer = setTimeout(() => {
-      setVisible(true)
-      hasShownThisLoad = true
-    }, 2000)
+      setVisible(true);
+      hasShownThisLoad = true;
+    }, 2000);
 
-    return () => clearTimeout(timer)
-  }, [isAnon])
+    return () => clearTimeout(timer);
+  }, [isAnon]);
 
   if (!isAnon || isDismissed || !visible) {
-    return null
+    return null;
   }
 
   const handleSignUp = () => {
-    window.location.href = withBasePath('/signup')
-  }
+    window.location.href = withBasePath("/signup");
+  };
 
   const handleDismiss = () => {
-    setIsDismissed(true)
-  }
+    setIsDismissed(true);
+  };
 
   return (
-    <div
-      className={`guest-banner ${className || ''}`}
-      role="status"
-      aria-live="polite"
-    >
+    <div className={`guest-banner ${className || ""}`} role="status" aria-live="polite">
       <div className="guest-banner-content">
         <div className="guest-banner-text">
-          <div className="guest-banner-title">
-            {t('guestBanner.title', "You're using Stirling PDF as a guest!")}
-          </div>
+          <div className="guest-banner-title">{t("guestBanner.title", "You're using Stirling PDF as a guest!")}</div>
           <div className="guest-banner-message">
-            {t('guestBanner.message', 'Create a free account to save your work, access more features, and support the project.')}
+            {t(
+              "guestBanner.message",
+              "Create a free account to save your work, access more features, and support the project.",
+            )}
           </div>
         </div>
         <div className="guest-banner-actions">
           <button
             onClick={handleDismiss}
-            aria-label={t('guestBanner.dismiss', 'Dismiss banner')}
+            aria-label={t("guestBanner.dismiss", "Dismiss banner")}
             className="guest-banner-dismiss"
           >
             <CloseIcon className="guest-banner-icon" />
           </button>
-          <button
-            onClick={handleSignUp}
-            className="guest-banner-signup"
-          >
+          <button onClick={handleSignUp} className="guest-banner-signup">
             <PersonAddIcon className="guest-banner-signup-icon" />
-            {t('guestBanner.signUp', 'Sign Up Free')}
+            {t("guestBanner.signUp", "Sign Up Free")}
           </button>
         </div>
       </div>
     </div>
-  )
+  );
 }
 
-export default GuestUserBanner
+export default GuestUserBanner;