Show full device token in admin panel

- API now returns full registration_id instead of truncated version
- Added Device Token column to devices table in admin panel
- Device tokens are displayed with word-wrap for long tokens
- Added Devices link to sidebar navigation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

internal/admin/handlers/device_handler.go

@@ -96,7 +96,7 @@ func (h *AdminDeviceHandler) ListAPNS(c *gin.Context) {
 			UserID:         device.UserID,
 			Username:       username,
 			DeviceID:       device.DeviceID,
-			RegistrationID: device.RegistrationID[:min(20, len(device.RegistrationID))] + "...",
+			RegistrationID: device.RegistrationID, // Full device token
 			DateCreated:    device.DateCreated.Format("2006-01-02T15:04:05Z"),
 		}
 	}
@@ -153,7 +153,7 @@ func (h *AdminDeviceHandler) ListGCM(c *gin.Context) {
 			UserID:           device.UserID,
 			Username:         username,
 			DeviceID:         device.DeviceID,
-			RegistrationID:   device.RegistrationID[:min(20, len(device.RegistrationID))] + "...",
+			RegistrationID:   device.RegistrationID, // Full device token
 			CloudMessageType: device.CloudMessageType,
 			DateCreated:      device.DateCreated.Format("2006-01-02T15:04:05Z"),
 		}