feat(reader): comic treatment for fixed-layout items in comics/manga libraries

PDFs shelved in comics or manga libraries (scanned manga, official manga
PDFs with text layers) now get comic reader treatment: bookmarks only —
no text-selection highlights, no annotations, no in-book search. Items
in ebooks libraries are completely unaffected, and EPUBs keep their
existing behavior everywhere.

- handlers: new exported ShouldTreatAsComic(libraryType, formatGroup) —
  true for fixed_layout/comic_archive in manga/comics libraries; the
  reader JSON API also exposes it as treat_as_comic
- router: the SSR reader page fetches the library type and passes
  TreatAsComic through ReaderMetadata into the init config
- reader: when treatAsComic is set, the PDF textLayer selection listener
  (mouse and touch paths) never attaches so no highlight popover can
  open; pointer mode is forced to pan (Smart/Text segment hidden);
  search button and toggleSearch are disabled; previously-created PDF
  highlights stop rendering
- bookmarks are unchanged (already page-index based for fixed layout),
  and device sync / OPDS / format classification are untouched since
  format_group stays fixed_layout

internal/handlers/reader.go

@@ -102,6 +102,7 @@ func (h *ReaderHandler) ShowReader(c *echo.Context) error {
 
 	// Determine if panel detection should be enabled
 	enablePanelDetection := shouldEnablePanelDetection(libraryWithType.TypeName, mediaItem.FormatGroup)
+	treatAsComic := ShouldTreatAsComic(libraryWithType.TypeName, mediaItem.FormatGroup)
 
 	// Get reading progress
 	var progress database.ReadingProgress
@@ -133,6 +134,7 @@ func (h *ReaderHandler) ShowReader(c *echo.Context) error {
 		"progress":               progress,
 		"bookmarks":              bookmarks,
 		"enable_panel_detection": enablePanelDetection,
+		"treat_as_comic":         treatAsComic,
 		"format_group":           mediaItem.FormatGroup,
 		"manga_type":             mediaItem.MangaType,
 		"reading_direction":      mediaItem.ReadingDirection,
@@ -639,6 +641,25 @@ func (h *ReaderHandler) ParseEbook(c *echo.Context) error {
 	})
 }
 
+// ShouldTreatAsComic reports whether a fixed-layout item that lives in a
+// comics or manga library should get comic reader treatment: bookmarks
+// only — no text-selection highlights, no annotations, no in-book search.
+// Comic archives already behave this way; this flag extends it to fixed-
+// layout PDFs shelved in comic libraries (scanned or official manga PDFs).
+func ShouldTreatAsComic(libraryType string, formatGroup string) bool {
+	comicLibraries := map[string]bool{
+		"manga":  true,
+		"comics": true,
+	}
+
+	fixedFormats := map[string]bool{
+		"fixed_layout":  true,
+		"comic_archive": true,
+	}
+
+	return comicLibraries[libraryType] && fixedFormats[formatGroup]
+}
+
 // shouldEnablePanelDetection determines if panel detection should be enabled
 // based on library type and format group
 func shouldEnablePanelDetection(libraryType string, formatGroup string) bool {