Phase 3 Week 7: Fix device auth middleware to set device object

- Update device auth middleware to set actual device object
- Change from DeviceContext to database.Devices
- Fix RequirePermission to use database.Devices
- Ensures handlers can access full device information
- Required for KOReader sync handlers to function properly

internal/middleware/device_auth.go

@@ -98,7 +98,8 @@ func (m *DeviceAuthMiddleware) Authenticate(next echo.HandlerFunc) echo.HandlerF
 			AutoSync:         device.AutoSync.Bool && device.AutoSync.Valid,
 		}
 
-		c.Set("device", ctx)
+		c.Set("device", device)
+		c.Set("device_ctx", ctx)
 		c.Set("device_id", device.ID.Bytes)
 		c.Set("user_id", device.UserID.Bytes)
 
@@ -119,7 +120,7 @@ func (m *DeviceAuthMiddleware) getRequestType(path string) string {
 func (m *DeviceAuthMiddleware) RequirePermission(permission string) echo.MiddlewareFunc {
 	return func(next echo.HandlerFunc) echo.HandlerFunc {
 		return func(c echo.Context) error {
-			device, ok := c.Get("device").(DeviceContext)
+			device, ok := c.Get("device").(database.Devices)
 			if !ok {
 				return c.JSON(http.StatusUnauthorized, map[string]string{
 					"error": "device not authenticated",