fix(ui): remove the broken Generate Cover button from the metadata editor

Generate Cover has never worked: it fetched the book file using a URL
scraped from the cover preview <img> tag (so it downloaded either the
existing cover JPEG or, when no cover existed, the detail page HTML),
then handed it to foliate-js, which rejects both. Its fixed-layout path
also called view.renderer.renderPage(), a method that does not exist in
the pinned foliate fork. Every click ended in the same generic 'Cover
generation failed' toast.

The working alternative already exists server-side: the scanner's
PDF/EPUB cover extraction plus the per-book Rescan button, now that the
rasterizer renders the CropBox. Users who want a specific image can
upload one.

Delete web/src/cover-generator.ts, the modal buttons, and the dead
generateCover()/coverGenerating/fileUrl plumbing in book-detail.ts.

web/src/book-detail.ts

@@ -1,6 +1,5 @@
 import { Alpine } from "./alpine";
 import { showToast } from "./toast";
-import { generateCoverBlob } from "./cover-generator";
 import { searchTagSuggestions, type TagSuggestion } from "./tag-dropdown";
 
 function getMediaId(): string {
@@ -91,7 +90,6 @@ export {
 
 interface MetadataEditorState {
   openSections: Record<string, boolean>;
-  coverGenerating: boolean;
   hasExistingCover: boolean;
   newCoverPreview: string;
   coverFile: Blob | null;
@@ -108,7 +106,6 @@ interface MetadataEditorState {
   showMetadataEditor(): void;
   hideMetadataEditor(): void;
   handleCoverUpload(event: Event): void;
-  generateCover(): Promise<void>;
   removeCover(): void;
   saveMetadata(): Promise<void>;
   rescanBook(): Promise<void>;
@@ -130,12 +127,6 @@ Alpine.data("bookDetail", () => {
     coverImg?.src &&
     !coverImg.src.includes("placeholder-book.svg");
 
-  const coverPreviewEl = document.querySelector(
-    ".aspect-\\[2\\/3\\] img",
-  ) as HTMLImageElement | null;
-  const coverSrc = coverPreviewEl?.src || "";
-  const fileUrl = coverSrc && !coverSrc.includes("placeholder") ? coverSrc : "";
-
   const initialTags: string[] = [];
   const tagBadges = document.querySelectorAll("#metadata-editor-modal [data-editor-tag]");
   tagBadges.forEach((el) => {
@@ -145,7 +136,6 @@ Alpine.data("bookDetail", () => {
 
   return {
     openSections: { basic: true } as Record<string, boolean>,
-    coverGenerating: false,
     hasExistingCover: !!hasCover,
     newCoverPreview: "",
     coverFile: null as Blob | null,
@@ -462,33 +452,6 @@ Alpine.data("bookDetail", () => {
       reader.readAsDataURL(file);
     },
 
-    async generateCover() {
-      this.coverGenerating = true;
-      try {
-        const formatGroup =
-          document
-            .querySelector('[data-format-group]')
-            ?.getAttribute("data-format-group") || "reflowable";
-
-        const blob = await generateCoverBlob(fileUrl, formatGroup);
-        if (!blob) return;
-
-        this.coverFile = blob;
-        this.coverAction = "upload";
-
-        const preview = document.getElementById(
-          "metadata-cover-preview",
-        ) as HTMLImageElement;
-        if (preview) {
-          preview.src = URL.createObjectURL(blob);
-        }
-        this.newCoverPreview = URL.createObjectURL(blob);
-        showToast("Cover generated successfully", "success");
-      } finally {
-        this.coverGenerating = false;
-      }
-    },
-
     removeCover() {
       this.coverAction = "remove";
       this.coverFile = null;

web/src/cover-generator.ts

@@ -1,82 +0,0 @@
-import { showToast } from "./toast";
-
-function getToken(): string {
-  return localStorage.getItem("token") || "";
-}
-
-export async function generateCoverBlob(
-  fileUrl: string,
-  formatGroup: string,
-): Promise<Blob | null> {
-  try {
-    const View = (await import("foliate-js/view.js")).default;
-    const view = new View();
-
-    const resp = await fetch(fileUrl, {
-      headers: { Authorization: `Bearer ${getToken()}` },
-    });
-    if (!resp.ok) {
-      showToast("Failed to fetch book file for cover generation", "error");
-      return null;
-    }
-
-    const blob = await resp.blob();
-    const file = new File([blob], "book", { type: blob.type });
-
-    const pdfOptions =
-      formatGroup === "fixed_layout"
-        ? {
-            pdf: {
-              cMapUrl: "/static/vendor/pdfjs/cmaps/",
-              standardFontDataUrl: "/static/vendor/pdfjs/standard_fonts/",
-            },
-          }
-        : {};
-
-    await view.open(file, pdfOptions);
-
-    if (!view.book?.sections?.length) {
-      showToast("Could not read book sections", "error");
-      return null;
-    }
-
-    if (formatGroup === "fixed_layout") {
-      const canvas = document.createElement("canvas");
-      await view.renderer?.renderPage(view.book.sections[0], canvas);
-      return new Promise((resolve) => {
-        canvas.toBlob(
-          (b) => resolve(b),
-          "image/jpeg",
-          0.85,
-        );
-      });
-    }
-
-    const coverHref = view.book.cover;
-    if (coverHref) {
-      const coverBlob = await coverHref.blob();
-      if (coverBlob.type.startsWith("image/")) {
-        return coverBlob;
-      }
-      return new Promise((resolve) => {
-        const img = new Image();
-        img.onload = () => {
-          const c = document.createElement("canvas");
-          c.width = img.naturalWidth;
-          c.height = img.naturalHeight;
-          c.getContext("2d")?.drawImage(img, 0, 0);
-          c.toBlob((b) => resolve(b), "image/jpeg", 0.85);
-        };
-        img.onerror = () => resolve(null);
-        img.src = URL.createObjectURL(coverBlob);
-      });
-    }
-
-    showToast("No cover found in book file", "error");
-    return null;
-  } catch (e) {
-    console.error("Cover generation failed:", e);
-    showToast("Cover generation failed", "error");
-    return null;
-  }
-}