refactor(ranking): replace blob cache with per-item PocketBase storage

- Replace SetRanking/GetRanking/SetRankingPageHTML/GetRankingPageHTML blob methods
  with WriteRankingItem/ReadRankingItems/RankingFreshEnough per-item operations
- Add 24h staleness gate in ScrapeRanking to skip re-scraping fresh data
- Add GET /api/ranking endpoint returning []RankingItem sorted by rank
- Remove RankingPageCacher interface and rankingCacheAdapter adapter
- Update integration tests to use new per-item upsert semantics
- Include e2e test suite (scraper/internal/e2e/)

scraper/internal/storage/store.go

@@ -5,7 +5,6 @@ package storage
 
 import (
 	"context"
-	"os"
 	"time"
 
 	"github.com/libnovel/scraper/internal/scraper"
@@ -22,14 +21,15 @@ type ChapterInfo struct {
 
 // RankingItem represents a single entry in the novel ranking list.
 type RankingItem struct {
-	Rank      int      `json:"rank"`
-	Slug      string   `json:"slug"`
-	Title     string   `json:"title"`
-	Author    string   `json:"author,omitempty"`
-	Cover     string   `json:"cover,omitempty"`
-	Status    string   `json:"status,omitempty"`
-	Genres    []string `json:"genres,omitempty"`
-	SourceURL string   `json:"source_url,omitempty"`
+	Rank      int       `json:"rank"`
+	Slug      string    `json:"slug"`
+	Title     string    `json:"title"`
+	Author    string    `json:"author,omitempty"`
+	Cover     string    `json:"cover,omitempty"`
+	Status    string    `json:"status,omitempty"`
+	Genres    []string  `json:"genres,omitempty"`
+	SourceURL string    `json:"source_url,omitempty"`
+	Updated   time.Time `json:"updated,omitempty"`
 }
 
 // ReadingProgress holds a single user's reading position for one book.
@@ -81,22 +81,13 @@ type Store interface {
 
 	// ── Ranking ────────────────────────────────────────────────────────────
 
-	// WriteRanking persists the ranking list.
-	WriteRanking(ctx context.Context, items []RankingItem) error
-	// ReadRankingItems returns the stored ranking items.
+	// WriteRankingItem upserts a single ranking entry (keyed on Slug).
+	WriteRankingItem(ctx context.Context, item RankingItem) error
+	// ReadRankingItems returns all ranking items sorted by rank ascending.
 	ReadRankingItems(ctx context.Context) ([]RankingItem, error)
-	// RankingFileInfo returns os.FileInfo-like data for the ranking record.
-	// Returns (nil, nil) when no ranking has been stored yet.
-	RankingFileInfo(ctx context.Context) (os.FileInfo, error)
-
-	// ── Ranking page HTML cache ────────────────────────────────────────────
-
-	// WriteRankingPageCache stores raw HTML for a ranking page.
-	WriteRankingPageCache(ctx context.Context, page int, html string) error
-	// ReadRankingPageCache returns cached HTML for a ranking page, or "" on miss.
-	ReadRankingPageCache(ctx context.Context, page int) (string, error)
-	// RankingPageCacheInfo returns file-like info for a cached ranking page.
-	RankingPageCacheInfo(ctx context.Context, page int) (os.FileInfo, error)
+	// RankingFreshEnough returns true when ranking rows exist and the most
+	// recent Updated timestamp is within maxAge of now.
+	RankingFreshEnough(ctx context.Context, maxAge time.Duration) (bool, error)
 
 	// ── Audio cache ────────────────────────────────────────────────────────
 
@@ -104,6 +95,8 @@ type Store interface {
 	GetAudioCache(ctx context.Context, cacheKey string) (string, bool)
 	// SetAudioCache persists a Kokoro filename for cacheKey.
 	SetAudioCache(ctx context.Context, cacheKey, filename string) error
+	// PutAudio stores raw audio bytes under the given MinIO object key.
+	PutAudio(ctx context.Context, key string, data []byte) error
 
 	// ── Reading progress ───────────────────────────────────────────────────