build: add Linux and Windows build scripts with NSIS installer

build-linux.sh configures and builds via CMake. build-windows.sh builds
in MSYS2/MINGW64, bundles Qt and transitive MinGW DLLs via windeployqt
plus an ldd pass, and produces an NSIS installer (installer.nsi). Ignore
the dist/ output and generated Setup.exe.

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

installer.nsi

@@ -0,0 +1,78 @@
+; NSIS installer for Ultimate Media Tracker
+;
+; Build with:  makensis installer.nsi
+; Expects the packaged app in the dist\ folder (produced by build-windows.sh).
+
+Unicode true
+
+!define APPNAME    "Ultimate Media Tracker"
+!define COMPANY    "UMT"
+!define VERSION    "1.0.0"
+!define EXE        "umt.exe"
+!define SOURCEDIR  "dist"
+!define REGUNINST  "Software\Microsoft\Windows\CurrentVersion\Uninstall\${APPNAME}"
+
+!include "MUI2.nsh"
+
+Name "${APPNAME}"
+OutFile "UltimateMediaTracker-Setup.exe"
+InstallDir "$PROGRAMFILES64\${APPNAME}"
+InstallDirRegKey HKLM "Software\${APPNAME}" "InstallDir"
+RequestExecutionLevel admin
+
+VIProductVersion "${VERSION}.0"
+VIAddVersionKey "ProductName"     "${APPNAME}"
+VIAddVersionKey "CompanyName"     "${COMPANY}"
+VIAddVersionKey "FileVersion"     "${VERSION}"
+VIAddVersionKey "FileDescription" "${APPNAME} Installer"
+VIAddVersionKey "LegalCopyright"  "${COMPANY}"
+
+!define MUI_ICON   "resources\icons\appicon.ico"
+!define MUI_UNICON "resources\icons\appicon.ico"
+
+!insertmacro MUI_PAGE_WELCOME
+!insertmacro MUI_PAGE_DIRECTORY
+!insertmacro MUI_PAGE_INSTFILES
+!define MUI_FINISHPAGE_RUN "$INSTDIR\${EXE}"
+!insertmacro MUI_PAGE_FINISH
+
+!insertmacro MUI_UNPAGE_CONFIRM
+!insertmacro MUI_UNPAGE_INSTFILES
+
+; First language listed is the default.
+!insertmacro MUI_LANGUAGE "German"
+!insertmacro MUI_LANGUAGE "English"
+
+Section "Install"
+    SetOutPath "$INSTDIR"
+    File /r "${SOURCEDIR}\*.*"
+
+    ; Shortcuts
+    CreateDirectory "$SMPROGRAMS\${APPNAME}"
+    CreateShortcut  "$SMPROGRAMS\${APPNAME}\${APPNAME}.lnk" "$INSTDIR\${EXE}" "" "$INSTDIR\${EXE}"
+    CreateShortcut  "$DESKTOP\${APPNAME}.lnk"               "$INSTDIR\${EXE}" "" "$INSTDIR\${EXE}"
+
+    ; Uninstaller + Add/Remove Programs entry
+    WriteUninstaller "$INSTDIR\Uninstall.exe"
+    WriteRegStr HKLM "Software\${APPNAME}" "InstallDir" "$INSTDIR"
+    WriteRegStr HKLM "${REGUNINST}" "DisplayName"     "${APPNAME}"
+    WriteRegStr HKLM "${REGUNINST}" "DisplayVersion"  "${VERSION}"
+    WriteRegStr HKLM "${REGUNINST}" "DisplayIcon"     "$INSTDIR\${EXE}"
+    WriteRegStr HKLM "${REGUNINST}" "Publisher"       "${COMPANY}"
+    WriteRegStr HKLM "${REGUNINST}" "UninstallString" "$INSTDIR\Uninstall.exe"
+    WriteRegDWORD HKLM "${REGUNINST}" "NoModify" 1
+    WriteRegDWORD HKLM "${REGUNINST}" "NoRepair" 1
+SectionEnd
+
+Section "Uninstall"
+    Delete "$SMPROGRAMS\${APPNAME}\${APPNAME}.lnk"
+    RMDir  "$SMPROGRAMS\${APPNAME}"
+    Delete "$DESKTOP\${APPNAME}.lnk"
+
+    ; Removes the program files only. User library/settings live in
+    ; %APPDATA%\UMT and are intentionally left untouched.
+    RMDir /r "$INSTDIR"
+
+    DeleteRegKey HKLM "${REGUNINST}"
+    DeleteRegKey HKLM "Software\${APPNAME}"
+SectionEnd