Add SMS gating, TCPA terms agreement, and compose-before-send modal

- Three-tier SMS gate: platform kill-switch → admin force-disable → plan AllowSms → company opt-in
- CompanySmsAgreement entity records admin acceptance of TCPA terms with IP, user agent, and terms version
- SMS terms of service modal on Company Settings with versioned re-agreement (AppConstants.SmsTermsVersion)
- Dev redirect: non-production SMS routed to Twilio:DevRedirectPhone to protect real customer numbers
- Removed redundant Ready for Pickup SMS (Job Completed covers it)
- Role-based compose modal on job completion: Admin/Manager reviews and edits before send; ShopFloor auto-sends
- Send SMS button on job details for ad-hoc messages (Admin/Manager only)
- SendJobSmsAsync auto-appends STOP opt-out language if missing
- Migrations: AddSmsGating, AddCompanySmsAgreement

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/PowderCoating.Core/Interfaces/IUnitOfWork.cs

@@ -9,6 +9,7 @@ public interface IUnitOfWork : IDisposable
     IRepository<Company> Companies { get; }
     IRepository<CompanyOperatingCosts> CompanyOperatingCosts { get; }
     IRepository<CompanyPreferences> CompanyPreferences { get; }
+    IRepository<CompanySmsAgreement> CompanySmsAgreements { get; }
 
     // AI Predictions
     IRepository<AiItemPrediction> AiItemPredictions { get; }