Setup and activate virtual environment via flake

When using the nix flake to generate a development shell, the python
virtual environment will now automatically be created and dependecies
from both requirements.txt and requirements-dev.txt will be installed.
This removes the need for using the setup script after entering the
dev shell. Exec bash must be the last thing called, as any other
commands past it will not get executed by the shell hook. Also removes
some duplicate dependencies that I found.

flake.nix

@@ -1,4 +1,6 @@
 {
+  description = "Tag Studio Development Environment";
+
   inputs = {
     nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
 
@@ -15,6 +17,9 @@
     qt6Pkgs = qt6Nixpkgs.legacyPackages.x86_64-linux;
   in {
     devShells.x86_64-linux.default = pkgs.mkShell {
+      name = "Tag Studio Virtual Environment";
+      venvDir = "./.venv";
+
       LD_LIBRARY_PATH = pkgs.lib.makeLibraryPath [
         pkgs.gcc-unwrapped
         pkgs.zlib
@@ -35,18 +40,17 @@
         qt6Pkgs.qt6.full
         qt6Pkgs.qt6.qtbase
       ];
+
       buildInputs = with pkgs; [
         cmake
         gdb
         zstd
-        python312Packages.pip
         python312Full
-        python312Packages.virtualenv # run virtualenv .
+        python312Packages.pip
         python312Packages.pyusb # fixes the pyusb 'No backend available' when installed directly via pip
+        python312Packages.venvShellHook # Initializes a venv in $venvDir
 
         libgcc
-        makeWrapper
-        bashInteractive
         glib
         libxkbcommon
         freetype
@@ -70,14 +74,31 @@
         # this is for the shellhook portion
         qt6Pkgs.qt6.wrapQtAppsHook
       ];
+
+      # Run after the virtual environment is created
+      postVenvCreation = ''
+        unset SOURCE_DATE_EPOCH
+
+        echo Installing dependencies into virtual environment
+        pip install -r requirements.txt
+        pip install -r requirements-dev.txt
+      '';
+
       # set the environment variables that Qt apps expect
-      shellHook = ''
+      postShellHook = ''
+        unset SOURCE_DATE_EPOCH
+
         export QT_QPA_PLATFORM=wayland
         export LIBRARY_PATH=/usr/lib:/usr/lib64:$LIBRARY_PATH
         # export LD_LIBRARY_PATH=${pkgs.stdenv.cc.cc.lib}/lib/:/run/opengl-driver/lib/
         export QT_PLUGIN_PATH=${pkgs.qt6.qtbase}/${pkgs.qt6.qtbase.qtPluginPrefix}
         bashdir=$(mktemp -d)
         makeWrapper "$(type -p bash)" "$bashdir/bash" "''${qtWrapperArgs[@]}"
+
+        echo Activating Virtual Environment
+        source $venvDir/bin/activate
+        export PYTHONPATH=$PWD/$venvDir/${pkgs.python312Full.sitePackages}:$PYTHONPATH
+
         exec "$bashdir/bash"
       '';
     };