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/handlers/handlers.go

@@ -6,6 +6,7 @@ import (
 	"log"
 	"net"
 	"net/http"
+	"strconv"
 	"strings"
 	"syscall"
 
@@ -15,28 +16,45 @@ import (
 
 	"booklib/internal/auth"
 	"booklib/internal/config"
-	"booklib/internal/redispkg"
-	"booklib/internal/scanner"
-	"booklib/internal/store"
-	"booklib/internal/upload"
+	"booklib/internal/ports"
 )
 
+// H 只依赖 ports 里的小口径接口(Task 25):具体实现由 main.go 装配,
+// 测试可注入手写 fake(portsfake),无需 PG/Redis。
 type H struct {
-	cfg *config.Config
-	st  *store.Store
-	rdb *redispkg.R
-	sc  *scanner.Scanner
-	up  *upload.U
+	cfg       *config.Config
+	users     ports.UserStore
+	libs      ports.LibraryStore
+	books     ports.BookStore
+	progress  ports.ProgressStore
+	bookmarks ports.BookmarkStore
+	rl        ports.RateLimiter
+	sc        ports.Scanner
+	med       ports.Media
+	up        ports.UploadSessions
 }
 
-func New(cfg *config.Config, st *store.Store, rdb *redispkg.R, sc *scanner.Scanner, up *upload.U) *H {
-	return &H{cfg: cfg, st: st, rdb: rdb, sc: sc, up: up}
+func New(cfg *config.Config, users ports.UserStore, libs ports.LibraryStore, books ports.BookStore,
+	progress ports.ProgressStore, bookmarks ports.BookmarkStore, rl ports.RateLimiter,
+	sc ports.Scanner, med ports.Media, up ports.UploadSessions) *H {
+	return &H{cfg: cfg, users: users, libs: libs, books: books, progress: progress,
+		bookmarks: bookmarks, rl: rl, sc: sc, med: med, up: up}
 }
 
 func err(c *gin.Context, status int, code, msg string) {
 	c.AbortWithStatusJSON(status, gin.H{"error": gin.H{"code": code, "message": msg}})
 }
 
+// idParam 解析 :id 路径参数,失败已回复 400。
+func idParam(c *gin.Context) (int64, bool) {
+	id, e := strconv.ParseInt(c.Param("id"), 10, 64)
+	if e != nil {
+		err(c, http.StatusBadRequest, "bad_request", "bad id")
+		return 0, false
+	}
+	return id, true
+}
+
 // dbErr 统一处理 store 层失败:记日志;连接类错误 503(Service Unavailable),其余 500
 // 注:brief 里的 pgxpool.ErrClosedPool 在 pgx v5 不存在,实际由 puddle 原样透出,用它替代;
 // PG 停机时池内连接先收到 SQLSTATE 57P01(administrator shutdown),故把 08xx/57Pxx 也归为 503