Fix AI quote blast rate: single formula path, correct client preview

Root cause: company-settings-lookups.js had its own baseByCfm/multiplier
tables that were completely different from ShopCapabilityCalculator.cs,
so the UI showed an inflated rate (e.g. 82 sqft/hr) while the AI prompt
received the server-computed rate (e.g. 9 sqft/hr).

- Add CompanySettingsController.DeriveBlastRate endpoint — thin GET that
  calls ShopCapabilityCalculator directly; now the single formula path
- Delete all client-side formula code (baseByCfm, multiplier tables,
  deriveBlastRate) — ~30 lines removed
- Modal live preview calls /CompanySettings/DeriveBlastRate with 250ms
  debounce instead of computing locally
- Blast setup table uses setup.derivedRate from GetBlastSetups (already
  server-computed) instead of recalculating client-side
- QuotesController.AiAnalyzeItem: when no blast setup is explicitly
  selected, fall back to the company's default blast setup so the
  configured rate is always used

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

src/PowderCoating.Web/wwwroot/js/item-wizard.js

@@ -1510,8 +1510,11 @@ async function aiAnalyze() {
     document.getElementById('ai_resultsSection')?.classList.add('d-none');
     document.getElementById('ai_errorAlert')?.classList.add('d-none');
 
-    const blastSetupIdEl = document.getElementById('ai_blastSetupId');
-    const blastSetupId   = blastSetupIdEl ? (parseInt(blastSetupIdEl.value) || null) : null;
+    const blastSetupIdEl  = document.getElementById('ai_blastSetupId');
+    const _defaultSetup   = blastSetupData.find(s => s.isDefault) || blastSetupData[0];
+    const blastSetupId    = blastSetupIdEl
+        ? (parseInt(blastSetupIdEl.value) || null)
+        : (_defaultSetup ? _defaultSetup.id : null);
 
     const payload = {
         photoTempIds:        wz.ai.tempIds,
@@ -1590,8 +1593,11 @@ async function aiSendFollowup() {
     const weightLbs    = isNaN(weightLbsRaw) || weightLbsRaw <= 0 ? null : weightLbsRaw;
     wz.data.quantity = qty;  // persist before renderStep re-renders
 
-    const blastSetupIdEl2 = document.getElementById('ai_blastSetupId');
-    const blastSetupId2   = blastSetupIdEl2 ? (parseInt(blastSetupIdEl2.value) || null) : null;
+    const blastSetupIdEl2  = document.getElementById('ai_blastSetupId');
+    const _defaultSetup2   = blastSetupData.find(s => s.isDefault) || blastSetupData[0];
+    const blastSetupId2    = blastSetupIdEl2
+        ? (parseInt(blastSetupIdEl2.value) || null)
+        : (_defaultSetup2 ? _defaultSetup2.id : null);
 
     const payload = {
         photoTempIds:        wz.ai.tempIds,