Catalog seeding, blank-unique fix, slides rotation, console repair

deploy/windows/installer/shopdb-install.ps1

@@ -127,6 +127,10 @@ param(
     # client reads as 127.0.0.1: the GE-Enforce IP allowlist, the dashboard
     # visitor-location lookup and per-host login rate limiting all break quietly.
     [ValidateSet('direct','proxy')] [string] $ClientIpSource = 'direct',
+    # Load the shared vendor/model catalog during stage 3. Offered by the
+    # wizard rather than assumed: a site that machines nothing does not want
+    # 21 machine types cluttering its dropdowns.
+    [switch] $SeedCatalog,
     # Required before this installer will alter an installation it did not
     # create. Everything here is built for a greenfield server: it makes its own
     # Python, its own venv and its own IIS objects, and its upgrade path assumes
@@ -1747,6 +1751,14 @@ build to get a matching pair, then send the install log to support.
             Invoke-Native $Flask @('seed',$seed) "seed $seed"
         }
 
+        # Additive and idempotent, so a re-run adds only what is genuinely new
+        # and never overwrites a description somebody corrected here.
+        if ($SeedCatalog) {
+            Write-Log 'flask seed catalog   (shared vendor and model catalog)'
+            $catalogOut = Invoke-Native $Flask @('seed','catalog') 'seed catalog' -OkExit 0,1
+            $catalogOut | Select-Object -Last 12 | ForEach-Object { Write-Log "    $_" }
+        }
+
         # Plugin registry starts empty on a fresh box. apply-profile resolves the
         # declared set's hard-dependency closure and installs + enables it in
         # dependency order, idempotently (ADR-013). It fails loudly if the profile