fix(installer): install the Visual C++ runtime before MySQL, and log the MSI

Second failure from the Server 2019 test. The previous fix worked - msiexec went
from exit 1639 (ERROR_INVALID_COMMAND_LINE, which is why it printed its usage
dialog) to exit 1603 (ERROR_INSTALL_FAILURE), so the command line parses now and
the MSI itself is failing.

It failed in 1.1 seconds. An MSI that dies that fast has not begun installing;
it has failed a launch condition. MySQL 8.4 requires the Visual C++
redistributable and a bare Windows Server does not ship it - the same runtime
mysql.exe and mysqldump.exe import, which was visible when their DLL
dependencies were trimmed and went unnoticed.

Stage 0 now installs VC_redist.x64.exe from the bundle before touching MySQL,
skipping it when vcruntime140.dll is already present, and fails with a sentence
naming the requirement if the redistributable is absent from the bundle
altogether. vcredist\ is an optional locked payload.

msiexec also gets /l*v now. A bare 1603 names neither the failing action nor the
reason, and it is the most common MySQL install failure - diagnosing this one
took a launch-condition inference rather than a log. The MSI log lands beside
the installer's own in ProgramData, so the next failure is readable instead of
guessed at.

deploy/windows/installer/build-installer.sh

@@ -82,7 +82,7 @@ done
 
 echo ""
 echo "Bundle staged at: $BUNDLE"
-for d in app wheels python httpplatformhandler urlrewrite mysqlclient mysql; do
+for d in app wheels python httpplatformhandler urlrewrite vcredist mysqlclient mysql; do
     if [ -d "$BUNDLE/$d" ]; then
         printf '  %-20s %s\n' "$d" "$(du -sh "$BUNDLE/$d" | cut -f1)"
     else
@@ -125,6 +125,7 @@ else
     echo "    python/              python-3.14.x-amd64.exe"
     echo "    httpplatformhandler/ httpPlatformHandler_amd64.msi"
     echo "    urlrewrite/          rewrite_amd64.msi       (client-IP rule; see README)"
+    echo "    vcredist/            VC_redist.x64.exe       (MySQL requires it)"
     echo "    mysql/               mysql-8.4.x-winx64.msi  (bundled-database option only)"
     echo ""
     echo "  If the payload changed ON PURPOSE, regenerate and COMMIT the lock:"