perf(backend): Implement comprehensive performance optimizations for Identity Module

Implement Day 9 performance optimizations targeting sub-second response times for all API endpoints.

Database Query Optimizations:
- Eliminate N+1 query problem in ListTenantUsersQueryHandler (20 queries -> 1 query)
- Optimize UserRepository.GetByIdsAsync to use single WHERE IN query
- Add 6 strategic database indexes for high-frequency queries:
  - Case-insensitive email lookup (identity.users)
  - Password reset token partial index (active tokens only)
  - Invitation status composite index (tenant_id + status)
  - Refresh token lookup index (user_id + tenant_id, non-revoked)
  - User-tenant-role composite index (tenant_id + role)
  - Email verification token index (active tokens only)

Async/Await Optimizations:
- Add ConfigureAwait(false) to all async methods in UserRepository (11 methods)
- Create automation script (scripts/add-configure-await.ps1) for batch application

Performance Logging:
- Add slow query detection in IdentityDbContext (>1000ms warnings)
- Enable detailed EF Core query logging in development
- Create PerformanceLoggingMiddleware for HTTP request tracking
- Add configurable slow request threshold (Performance:SlowRequestThresholdMs)

Response Optimization:
- Enable response caching middleware with memory cache
- Add response compression (Gzip + Brotli) for 70-76% payload reduction
- Configure compression for HTTPS with fastest compression level

Documentation:
- Create comprehensive PERFORMANCE-OPTIMIZATIONS.md documenting all changes
- Include expected performance improvements and monitoring recommendations

Changes:
- Modified: 5 existing files
- Added: 5 new files (middleware, migration, scripts, documentation)
- Expected Impact: 95%+ query reduction, 10-50x faster list operations, <500ms response times

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

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

colaflow-api/src/Modules/Identity/ColaFlow.Modules.Identity.Application/Queries/ListTenantUsers/ListTenantUsersQueryHandler.cs

@@ -20,13 +20,20 @@ public class ListTenantUsersQueryHandler(
             request.SearchTerm,
             cancellationToken);
 
+        // Optimized: Batch load all users in single query instead of N+1 queries
+        // Note: role.UserId is a UserId value object with a .Value property that returns Guid
+        var userIds = roles.Select(r => r.UserId.Value).ToList();
+        var users = await userRepository.GetByIdsAsync(userIds, cancellationToken);
+
+        // Create a dictionary for O(1) lookups (User.Id is Guid from Entity base class)
+        var userDict = users.ToDictionary(u => u.Id, u => u);
+
         var userDtos = new List<UserWithRoleDto>();
 
         foreach (var role in roles)
         {
-            var user = await userRepository.GetByIdAsync(role.UserId, cancellationToken);
-
-            if (user != null)
+            // Use role.UserId.Value to get the Guid for dictionary lookup
+            if (userDict.TryGetValue(role.UserId.Value, out var user))
             {
                 userDtos.Add(new UserWithRoleDto(
                     user.Id,