refactor(cards): H2 foundation — cards.go, the one BookInfo construction site

BookInfo, LibraryTypeMap, and MediaBadgeKind move verbatim out of
collections.go into handlers/cards.go (the card package surface, same
package: no import-graph or templ changes), joined by the H2 builder:

- buildBookCard (unexported): the ONLY place BookInfo is constructed,
  fed by cardSource; cover URL via ResolveMediaURL, badge via
  MediaBadgeKind — both inside the builder, not per call site.
- Four exported adapters normalize the four real feed shapes:
  database.MediaItems (sections/smart/series/tags/preview),
  GetCollectionItemsForDashboardRow (collection dashboard branch),
  GetCollectionItemsRow (collection-items joins — MediaItemID field),
  SearchMediaItemsUnifiedRow (badge rides its LibraryTypeName column,
  so no LibraryTypeMap query at all).
- Adapters return non-nil empty slices, which retires the per-site
  []BookInfo{} empty-seed assignments when call sites migrate.

No call site changes in this commit — the 20 literals and 5 seeds are
migrated one surface per commit next, each with the H0 pin suite.

Verified: build, vet (only the two pre-existing flagged saveCoverImage
warnings), and 14/14 contract pins — the key freeze is byte-identical.

internal/handlers/collections.go

@@ -5,7 +5,6 @@ import (
 	"bookhoard/internal/services"
 	wsync "bookhoard/internal/sync"
 	"bookhoard/internal/utils"
-	"context"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -70,55 +69,6 @@ type UpdateDeviceMappingRequest struct {
 	SyncDirection   string `json:"sync_direction" validate:"required,oneof=bidirectional book_to_device device_to_book none"`
 }
 
-type BookInfo struct {
-	MediaItemID    string `json:"media_item_id"`
-	Title          string `json:"title"`
-	Author         string `json:"author"`
-	CoverImagePath string `json:"cover_image_path"`
-	HasConflict    bool   `json:"has_conflict"`
-	// Media-type identifier for card badges/hover icons (A2c)
-	FormatGroup string `json:"format_group"`
-	// Resolved cover-badge glyph: "audiobook" | "comic" | "manga" | "".
-	// comic vs manga rides the LIBRARY type (format_group only knows
-	// comic_archive — manga_type is unreliable across sources).
-	Badge string `json:"badge"`
-}
-
-// LibraryTypeMap builds libraryID→library-type-name for badge resolution
-// (one small query per request; libraries are few).
-func LibraryTypeMap(ctx context.Context, db *database.Queries) map[string]string {
-	m := map[string]string{}
-	libs, err := db.ListLibraries(ctx)
-	if err != nil {
-		return m
-	}
-	for _, l := range libs {
-		if l.ID.Valid {
-			m[uuid.UUID(l.ID.Bytes).String()] = l.TypeName
-		}
-	}
-	return m
-}
-
-// MediaBadgeKind resolves the badge glyph per media type from the row's
-// format group and its library's type name. The library type is
-// authoritative for the comic/manga split: manga volumes ship as
-// fixed_layout scans (image PDFs) just as often as comic_archive, and
-// manga_type is unreliable across sources (unknown/NULL on real rows),
-// so anything in a manga library reads manga, anything in a comics
-// library reads comic, and a stray comic_archive elsewhere still does.
-func MediaBadgeKind(formatGroup, libraryTypeName string) string {
-	switch {
-	case formatGroup == "audiobook":
-		return "audiobook"
-	case libraryTypeName == "manga":
-		return "manga"
-	case formatGroup == "comic_archive" || libraryTypeName == "comics":
-		return "comic"
-	}
-	return ""
-}
-
 type SectionData struct {
 	ID           string     `json:"id"`
 	CollectionID string     `json:"collection_id"`