feat: update login flow and add firework effects

- Update mobile HomeView to show WeChat scan login instructions
- Remove manual name/department input form from mobile client
- Add firework particle effects to big screen background
- Remove department field from login flow types

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/shared/src/types/scan-login.types.ts

@@ -11,7 +11,6 @@ export interface ScanTokenData {
   userInfo?: {
     userId: string;
     userName: string;
-    department: string;
   };
 }
 
@@ -38,7 +37,6 @@ export interface ValidateTokenResponse {
 export interface ScanConfirmPayload {
   scanToken: string;
   userName: string;
-  department: string;
 }
 
 export interface ScanConfirmResponse {
@@ -56,7 +54,6 @@ export interface ScanStatusUpdatePayload {
   userInfo?: {
     userId: string;
     userName: string;
-    department: string;
     sessionToken: string;
   };
 }