Fix static field mutation in CrystaProgramSyncModuleService constructor

[Copilot]

The service constructor was writing to a static field, causing thread-safety issues and defeating transient DI registration. Multiple service instances shared the same static _modules list, leading to race conditions.

Changes:

• Converted to singleton with factory pattern: Changed from AppDbContext injection to IDbContextFactory<AppDbContext>, enabling singleton lifetime with scoped DbContext creation
• Removed static fields: Made _modules instance-based with thread-safe lazy initialization using SemaphoreSlim
• Added proper disposal: Implemented IDisposable to cleanup semaphore resources
• Fixed cancellation propagation: Added CancellationToken parameter to UpdateSyncModuleAsync interface and propagated through all async operations

Before:

public class CrystaProgramSyncModuleService {
    private static List<CrystaProgramSyncModule> _modules = new();
    
    public CrystaProgramSyncModuleService(AppDbContext dbContext) {
        if (_modules.Count == 0) {
            _modules = dbContext.Set<CrystaProgramSyncModule>()...;  // ❌ Static mutation
        }
    }
}

services.AddTransient<ICrystaProgramSyncModuleService, ...>();  // ❌ Wrong lifetime

After:

public class CrystaProgramSyncModuleService : IDisposable {
    private List<CrystaProgramSyncModule> _modules = new();
    private readonly SemaphoreSlim _initLock = new(1, 1);
    
    public CrystaProgramSyncModuleService(IDbContextFactory<AppDbContext> factory) {
        this.DbContextFactory = factory;
    }
    
    private async Task EnsureInitializedAsync(CancellationToken ct) {
        await _initLock.WaitAsync(ct);
        try {
            if (!_initialized) {
                await using var db = await DbContextFactory.CreateDbContextAsync(ct);
                _modules = await db.Set<CrystaProgramSyncModule>()...;
            }
        } finally { _initLock.Release(); }
    }
}

services.AddSingleton<ICrystaProgramSyncModuleService, ...>();  // ✓ Correct lifetime

Applied same pattern to CrystaProgramSyncModuleServiceFake.

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