Add SMS Agreements admin page and update help docs

- Add /SmsAgreements SuperAdmin page listing per-company SMS terms acceptance
  status, with stats cards, filter/search, and a full acceptance history modal
  (terms version, accepted by, timestamp, IP, user agent)
- Add SMS Agreements nav link under Tenants & Billing in the platform sidebar
- Update HelpKnowledgeBase and Help docs (Quotes, Settings) to document
  quote approval via SMS and the reuse of existing approval tokens

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

src/PowderCoating.Web/Views/Help/Settings.cshtml

@@ -393,6 +393,12 @@
             <h4 class="h6 fw-semibold mt-3 mb-2" style="font-size:.85rem;">What events send an SMS</h4>
             <ul class="mb-3">
                 <li class="mb-1"><strong>Job Completed</strong> — notifies the customer their job is done and ready for pickup.</li>
+                <li class="mb-1">
+                    <strong>Quote Approval Request</strong> — sends the customer a link to review and approve or decline
+                    their quote directly from their phone. Click <strong>Send Quote via SMS</strong> on any quote's Details
+                    page. If an email was already sent for the same quote, the existing approval link is reused so both
+                    delivery methods work simultaneously.
+                </li>
             </ul>
             <h4 class="h6 fw-semibold mt-3 mb-2" style="font-size:.85rem;">Compose-before-send vs. auto-send</h4>
             <p>