fix: backfill posters for ALL history entries; skip <img> when no poster

- backfill script deduped by slug_id, so a second entry for the same
  anime kept no poster -> rendered as a broken <img src="">
- re-backfilled from the already-fetched poster per slug
- showHome now only emits an <img> when the entry has a poster

static/app.js

@@ -76,8 +76,10 @@ function showHome() {
   const sec = el("section", "hero-sec");
   const card = el("a", "hero");
   card.href = histHref(hero);
-  const img = el("img"); img.src = hero.poster || ""; img.alt = "";
-  card.append(img);
+  if (hero.poster) {
+    const img = el("img"); img.src = hero.poster; img.alt = "";
+    card.append(img);
+  }
   const right = el("div", "right");
   const body = el("div", "hero-body");
   body.append(el("div", "hero-kicker", "continue watching"),
@@ -97,7 +99,10 @@ function showHome() {
     for (const x of history.slice(1, 6)) {
       const c = el("a", "card");
       c.href = histHref(x);
-      const i = el("img"); i.src = x.poster || ""; i.alt = "";
+      if (x.poster) {
+        const i = el("img"); i.src = x.poster; i.alt = "";
+        c.append(i);
+      }
       const info = el("div", "mini-info");
       info.append(el("div", "card-name", x.title));
       const meta = el("div", "mini-meta");
@@ -105,7 +110,7 @@ function showHome() {
       info.append(meta);
       const pb = bar(x, "small");
       if (pb) info.append(pb);
-      c.append(i, info);
+      c.append(info);
       grid.append(c);
     }
     main.append(grid);