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/README.md

@@ -53,6 +53,7 @@ bundle/wheels/               pip download -r requirements.txt --only-binary=:all
 bundle/python/               python-3.14.x-amd64.exe
 bundle/httpplatformhandler/  httpPlatformHandler_amd64.msi
 bundle/urlrewrite/           rewrite_amd64.msi        (client-IP rule; see below)
+bundle/vcredist/             VC_redist.x64.exe        (MySQL will not install without it)
 bundle/mysql/                mysql-8.4.x-winx64.msi   (bundled-database option only)
 bundle/mysqlclient/          mysql.exe, mysqldump.exe + libcrypto/libssl (backups)
 ```