feat(bookmarks): location identity, origin provenance, KOReader-style labels

- Drop UNIQUE(media_item_id,user_id,title): titles are display labels
  shared verbatim across clients; same-title bookmarks on different pages
  now coexist instead of 500ing (deleting over a tombstone no longer
  blocks future creates with that title)
- Add origin_source column recording the creating client (android/web/
  koreader), set once at insert, exposed in API responses
- Web reader auto-title mirrors KOReader's 'in <chapter>' convention,
  falling back to 'Bookmark'; adds bookmark rename in the drawer

web/src/reader/reader.ts

@@ -472,6 +472,8 @@ document.addEventListener("alpine:init", () => {
       positionLabel: string;
       cfi: string;
       page: number | null;
+      renameOpen?: boolean;
+      renameText?: string;
     }[],
     tocItems: [] as any[],
     mediaItemId: "" as string,
@@ -2079,6 +2081,14 @@ document.addEventListener("alpine:init", () => {
       const page = this.isFixedLayout
         ? (this.renderer?.index ?? 0) + 1
         : 0;
+      // Auto-label mirrors KOReader's convention ("in <chapter title>")
+      // so every client names unnamed bookmarks identically; falls back
+      // to a plain "Bookmark" for fixed-layout or TOC-less books.
+      const chapter = this.lastRelocateDetail?.tocItem?.label as
+        | string
+        | undefined;
+      const title =
+        !this.isFixedLayout && chapter ? `in ${chapter}` : "Bookmark";
 
       try {
         const resp = await fetch(
@@ -2090,7 +2100,7 @@ document.addEventListener("alpine:init", () => {
               "Content-Type": "application/json",
             },
             body: JSON.stringify({
-              title: `Bookmark at ${this.progressText || "current position"}`,
+              title,
               position: this.isFixedLayout
                 ? `page:${page}`
                 : cfi
@@ -2130,6 +2140,38 @@ document.addEventListener("alpine:init", () => {
         /* ignore bookmark errors for now */
       }
     },
+    startBookmarkRename(bookmark: (typeof this.bookmarkItems)[number]) {
+      bookmark.renameOpen = true;
+      bookmark.renameText = bookmark.title;
+    },
+    async renameBookmark(bookmark: (typeof this.bookmarkItems)[number]) {
+      const token = getToken();
+      const title = (bookmark.renameText ?? "").trim();
+      if (!token || !this.mediaItemId || !title) return;
+      try {
+        const resp = await fetch(
+          `/api/media-items/${this.mediaItemId}/bookmarks/${bookmark.id}`,
+          {
+            method: "PUT",
+            headers: {
+              Authorization: `Bearer ${token}`,
+              "Content-Type": "application/json",
+            },
+            body: JSON.stringify({
+              title,
+              notes: "",
+              position: bookmark.positionLabel || "",
+            }),
+          },
+        );
+        if (resp.ok) {
+          bookmark.title = title;
+        }
+        bookmark.renameOpen = false;
+      } catch (_e) {
+        bookmark.renameOpen = false;
+      }
+    },
     chapterNumberForProgress(): number {
       const tocItem = this.lastRelocateDetail?.tocItem;
       if (!tocItem?.label) return 0;