Validate screenshot URLs with inline hints

wwwroot/js/ui.js

@@ -520,6 +520,8 @@ function buildSuggestionForm(initial = {}, lockTitle = false) {
           <span class="char-counter" data-for="screenshotUrl"></span>
         </span>
         <input name="screenshotUrl" maxlength="2048" />
+        <p class="hint" data-i18n="form.screenshotHint">${t("form.screenshotHint")}</p>
+        <div class="form-error hidden" data-error="screenshot"></div>
       </label>
       <label class="stack">
         <span class="label-row">
@@ -618,6 +620,8 @@ function openSuggestionModal({ title, submitLabel, initial = {}, onSubmit, lockT
         const errorBox = form.querySelector('[data-error="players"]');
         const minInput = form.querySelector('input[name="minPlayers"]');
         const maxInput = form.querySelector('input[name="maxPlayers"]');
+        const screenshotError = form.querySelector('[data-error="screenshot"]');
+        const screenshotInput = form.querySelector('input[name="screenshotUrl"]');
         const markError = (msg) => {
             if (errorBox) {
                 errorBox.textContent = msg;
@@ -626,6 +630,7 @@ function openSuggestionModal({ title, submitLabel, initial = {}, onSubmit, lockT
         };
         const clearError = () => {
             if (errorBox) errorBox.classList.add("hidden");
+            if (screenshotError) screenshotError.classList.add("hidden");
         };
         clearError();
         const min = data.minPlayers;
@@ -643,8 +648,14 @@ function openSuggestionModal({ title, submitLabel, initial = {}, onSubmit, lockT
             return;
         }
         if (data.screenshotUrl && !isValidImageUrl(data.screenshotUrl)) {
-            return toast(t("toast.invalidImageUrl"), true);
+            if (screenshotError) {
+                screenshotError.textContent = t("form.screenshotInvalid");
+                screenshotError.classList.remove("hidden");
+            }
+            screenshotInput?.classList.add("input-error");
+            return;
         }
+        screenshotInput?.classList.remove("input-error");
         if (!data.name?.trim()) return toast(t("toast.nameRequired"), true);
         try {
             await onSubmit(data, close, submitBtn);
@@ -976,6 +987,23 @@ function isValidImageUrl(url) {
         const u = new URL(url);
         const allowed = ["http:", "https:"];
         if (!allowed.includes(u.protocol)) return false;
+        const host = u.hostname.toLowerCase();
+        const bannedHosts = [
+            "bit.ly",
+            "tinyurl.com",
+            "t.co",
+            "goo.gl",
+            "ow.ly",
+            "is.gd",
+            "buff.ly",
+            "rebrand.ly",
+            "steamcommunity.com",
+            "store.steampowered.com",
+            "imgur.com",
+        ];
+        if (bannedHosts.some((h) => host === h)) return false;
+        if (host === "imgur.com" && !u.pathname.startsWith("/a/") && !u.pathname.startsWith("/gallery/")) return false;
+        if (host === "steamcommunity.com") return false;
         const path = u.pathname.toLowerCase();
         return [".png", ".jpg", ".jpeg", ".gif", ".webp", ".avif"].some((ext) =>
             path.endsWith(ext),