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.Infrastructure/Data/ApplicationDbContext.cs

@@ -143,6 +143,9 @@ public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
     /// <summary>Tenant company records. Soft-delete only filter applies (no CompanyId filter — SuperAdmin manages all companies).</summary>
     public DbSet<Company> Companies { get; set; }
 
+    /// <summary>Immutable audit trail of SMS terms-of-service acceptances per company. Tenant-filtered by CompanyId; never soft-deleted.</summary>
+    public DbSet<CompanySmsAgreement> CompanySmsAgreements { get; set; }
+
     /// <summary>AI quote-item predictions; tenant-filtered. Both <c>QuoteItem</c> and <c>JobItem</c> share a single prediction record via nullable FK (no duplication on quote→job conversion).</summary>
     public DbSet<AiItemPrediction> AiItemPredictions { get; set; }