Remove ffmpeg from published Docker images (#6791)

## Summary

Published Docker images (`stirling-pdf:latest`, `:2.13.1`) still shipped
the full `ffmpeg` package even though it was disabled in source back in
#6053.

**Root cause:** `push-docker.yml` passed a hardcoded
`BASE_VERSION=1.0.0` build-arg for the regular image, overriding the
Dockerfile's `ARG BASE_VERSION=1.0.2` default. Base `1.0.0` is the
original base that still does the explicit `ffmpeg` apt install, so the
published image never picked up the removal.

.github/aur/stirling-pdf-desktop/PKGBUILD

@@ -1,6 +1,6 @@
 # Maintainer: Stirling PDF Inc <contact@stirlingpdf.com>
 pkgname=stirling-pdf-desktop
-pkgver=2.13.1
+pkgver=2.13.2
 pkgrel=1
 pkgdesc="Locally hosted, web-based PDF manipulation tool (Tauri desktop app, official Stirling PDF Inc build)"
 arch=('x86_64')

.github/aur/stirling-pdf-server-bin/PKGBUILD

@@ -1,6 +1,6 @@
 # Maintainer: Stirling PDF Inc <contact@stirlingpdf.com>
 pkgname=stirling-pdf-server-bin
-pkgver=2.13.1
+pkgver=2.13.2
 pkgrel=1
 pkgdesc="Locally hosted, web-based PDF manipulation tool (server JAR, prebuilt)"
 arch=('any')