feat(phase-a): remove Neo4j from startup chain, clean auth flow

- Remove NeoUserProvider + NeoInstituteProvider from App.tsx startup chain
- Strip user_db_name/school_db_name from CCUser; add school_id (Phase B wires it to Supabase)
- Remove DatabaseNameService from AuthContext and UserContext
- Remove provisionUser() call from login path; API endpoint preserved for Phase B decision
- Simplify UserContext.resolveProfile: fast-path JWT metadata then background Supabase fetch
- Replace user.user_db_name reads in singlePlayerPage + snapshotService with null-safe guards
- Add useDeviceContext hook (desktop/tablet/phone/iwb, persists to localStorage)

App now loads to dashboard without any Neo4j dependency at startup.
Canvas opens to blank TLDraw state; Phase B rebuilds navigation on Supabase.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

src/services/auth/authService.ts

@@ -3,7 +3,6 @@ import { TLUserPreferences } from '@tldraw/tldraw';
 import { supabase } from '../../supabaseClient';
 import { storageService, StorageKeys } from './localStorageService';
 import { logger } from '../../debugConfig';
-import { DatabaseNameService } from '../graph/databaseNameService';
 
 export interface CCUser {
   id: string;
@@ -11,8 +10,7 @@ export interface CCUser {
   user_type: string;
   username: string;
   display_name: string;
-  user_db_name: string;
-  school_db_name: string;
+  school_id?: string | null;
   created_at?: string;
   updated_at?: string;
 }
@@ -44,28 +42,13 @@ export function convertToCCUser(user: User, metadata: CCUserMetadata): CCUser {
   // Default to student if no user type specified
   const userType = metadata.user_type || 'student';
 
-  const storedUserDb = DatabaseNameService.getStoredUserDatabase();
-  const storedSchoolDb = DatabaseNameService.getStoredSchoolDatabase();
-
-  const userDbName = storedUserDb || DatabaseNameService.getUserPrivateDB(
-    userType,
-    user.id
-  );
-  const schoolDbName = metadata.school_db_name || metadata.worker_db_name || storedSchoolDb || '';
-
-  DatabaseNameService.rememberDatabaseNames({
-    userDbName,
-    schoolDbName
-  });
-
   return {
     id: user.id,
     email: user.email,
     user_type: userType,
-    username: username,
+    username,
     display_name: displayName,
-    user_db_name: userDbName,
-    school_db_name: schoolDbName,
+    school_id: null,
     created_at: user.created_at,
     updated_at: user.updated_at,
   };