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.Shared/Constants/AppConstants.cs

@@ -7,6 +7,12 @@ public static class AppConstants
 
     /// <summary>Set to true to enable SMS features throughout the UI.</summary>
     public const bool SmsEnabled = false;
+
+    /// <summary>
+    /// Current version of the SMS terms of service. Incrementing this string invalidates all
+    /// existing company agreements and forces company admins to re-accept before enabling SMS.
+    /// </summary>
+    public const string SmsTermsVersion = "1.0";
     
     public static class Roles
     {