refactor(router): update routes and middleware for Echo v5

Update all router files to use Echo v5 APIs and type signatures.

Changes in router.go:
- Replace echomiddleware.Logger() with RequestLogger() (line 144)
- Update import from echo/v4 to echo/v5

Changes in frontend.go:
- Update frontend handler signatures to use *echo.Context
- Fix middleware registration for v5 compatibility

Changes in auth.go, library.go, scanner.go, sync.go, helpers.go:
- Update handler function signatures to *echo.Context
- Ensure consistent type usage across all route handlers

All routes now properly implement Echo v5's middleware and handler patterns.

internal/router/scanner.go

@@ -2,7 +2,8 @@ package router
 
 import (
 	"bookhoard/internal/handlers"
-	"github.com/labstack/echo/v4"
+
+	"github.com/labstack/echo/v5"
 )
 
 // registerScannerRoutes registers all scanner-related endpoints