refactor(handlers): consume port interfaces, wire media+upload assembly (Task 25+26)

- H now holds only small port interfaces (UserStore/LibraryStore/BookStore/
  ProgressStore/BookmarkStore/RateLimiter/Scanner/Media/UploadSessions);
  NewRouter is the composition root distributing *store.Store and *redispkg.R
- ports.Media gains EnsurePage; ChaptersOf returns ports.Chapter (media's
  local duplicate dropped); *media.M now provably satisfies ports.Media;
  ports.UploadSessions gains LibraryID for root validation before Complete
- content.go: duplicated page-index cache + cover self-heal + page extract
  logic removed in favor of media service — same redis keys, same contract;
  path traversal check stays in handler (403 semantics preserved)
- getLibrary/getLibRow merged into getLib(c, id); idParam helper dedupes
  :id parsing; isUnique replaced by ports.IsUniqueViolation (Task 28 partial)
- main.go assembles media + upload and passes upload.U as scanner Sweeper

Full gate green: gofmt, vet, go test -p 1 (real PG+Redis, 0 skip)

backend/cmd/webui/api/router.go

@@ -7,15 +7,18 @@ import (
 
 	"booklib/cmd/webui/handlers"
 	"booklib/internal/config"
+	"booklib/internal/media"
 	"booklib/internal/redispkg"
 	"booklib/internal/scanner"
 	"booklib/internal/store"
 	"booklib/internal/upload"
 )
 
-func NewRouter(cfg *config.Config, st *store.Store, rdb *redispkg.R, sc *scanner.Scanner, up *upload.U) *gin.Engine {
+// NewRouter 是组合根:接受具体实现,分发给 handlers.New 的小口径 port 字段。
+// *store.Store 满足 5 个 store 接口,*redispkg.R 满足 RateLimiter。
+func NewRouter(cfg *config.Config, st *store.Store, rdb *redispkg.R, sc *scanner.Scanner, med *media.M, up *upload.U) *gin.Engine {
 	gin.SetMode(gin.ReleaseMode)
-	h := handlers.New(cfg, st, rdb, sc, up)
+	h := handlers.New(cfg, st, st, st, st, st, rdb, sc, med, up)
 	r := gin.New()
 	if e := r.SetTrustedProxies(cfg.TrustedProxies); e != nil {
 		panic(e)

backend/cmd/webui/api/router_test.go

@@ -16,7 +16,7 @@ func testCfg() *config.Config {
 }
 
 func TestHealthz(t *testing.T) {
-	r := NewRouter(testCfg(), nil, redispkg.New(""), nil, nil)
+	r := NewRouter(testCfg(), nil, redispkg.New(""), nil, nil, nil)
 	req := httptest.NewRequest(http.MethodGet, "/api/healthz", nil)
 	w := httptest.NewRecorder()
 	r.ServeHTTP(w, req)