feat(api): add collections and device mapping API endpoints

Add comprehensive API support for Phase 9 features:

Collections API (/api/collections):
- GET /collections: List all user collections
- POST /collections: Create new collection
- GET /collections/🆔 Get collection details
- PUT /collections/🆔 Update collection
- DELETE /collections/🆔 Delete collection
- GET /collections/:id/books: Get books in collection
- POST /collections/:id/books: Add books to collection
- DELETE /collections/:id/books/:bookId: Remove book from collection

Device Shelf Mapping API (/api/devices/:id/collections):
- GET: Get all collection-to-shelf mappings for device
- POST: Create new mapping
- PUT /:collectionId: Update mapping
- DELETE /:collectionId: Delete mapping

Book Matching API:
- POST /sync/books/query: Query books by identifiers
- POST /devices/:deviceId/sync/link-book: Manual book linking
- GET /devices/:deviceId/sync/unlinked-books: List unmatched books
- GET /devices/:id/file-aliases: Get device file aliases
- POST /devices/:id/file-aliases: Create file alias
- PUT /devices/:id/file-aliases/:aliasId: Update alias
- DELETE /devices/:id/file-aliases/:aliasId: Delete alias
- GET /books/match: Search for book matches

All new endpoints - no existing APIs modified.

internal/handlers/ebook.go

@@ -70,6 +70,35 @@ func parseDate(dateStr string) time.Time {
 func SetupRoutes(g *echo.Group, db *database.Queries, connManager *wsync.ConnectionManager) *Handler {
 	h := NewHandler(db, connManager)
 
+	// Collections API routes
+	collectionHandler := NewCollectionHandler(db)
+	collections := g.Group("/collections")
+	collections.GET("", collectionHandler.GetCollections)
+	collections.POST("", collectionHandler.CreateCollection)
+	collections.GET("/:id", collectionHandler.GetCollection)
+	collections.PUT("/:id", collectionHandler.UpdateCollection)
+	collections.DELETE("/:id", collectionHandler.DeleteCollection)
+	collections.GET("/:id/books", collectionHandler.GetBookCollections)
+	collections.POST("/:id/books", collectionHandler.AddBooks)
+	collections.DELETE("/:id/books/:bookId", collectionHandler.RemoveBook)
+
+	// Device shelf mapping routes
+	deviceCollections := g.Group("/devices/:id/collections")
+	deviceCollections.GET("", collectionHandler.GetDeviceMappings)
+	deviceCollections.POST("", collectionHandler.CreateDeviceMapping)
+	deviceCollections.PUT("/:collectionId", collectionHandler.UpdateDeviceMapping)
+	deviceCollections.DELETE("/:collectionId", collectionHandler.DeleteDeviceMapping)
+
+	// Book matching and linking routes
+	g.POST("/sync/books/query", h.QueryBooks)
+	g.POST("/devices/:deviceId/sync/link-book", h.LinkBook)
+	g.GET("/devices/:deviceId/sync/unlinked-books", h.GetUnlinkedBooks)
+	g.GET("/devices/:id/file-aliases", h.GetDeviceFileAliases)
+	g.POST("/devices/:id/file-aliases", h.CreateDeviceFileAlias)
+	g.PUT("/devices/:id/file-aliases/:aliasId", h.UpdateDeviceFileAlias)
+	g.DELETE("/devices/:id/file-aliases/:aliasId", h.DeleteDeviceFileAlias)
+	g.GET("/books/match", h.GetBookMatches)
+
 	// Media item routes (all authenticated users)
 	g.GET("/media-items", h.ListMediaItems)
 	g.GET("/media-items/filtered", h.ListMediaItemsFiltered)