add flake support

flake.nix

@@ -0,0 +1,73 @@
+{
+  description = "Backend development flake";
+  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
+  outputs = {nixpkgs, ... }: let
+    forAllSystems = nixpkgs.lib.genAttrs [
+      "aarch64-linux"
+      "i686-linux"
+      "x86_64-linux"
+      "aarch64-darwin"
+      "x86_64-darwin"
+    ];
+  in {
+    devShells = forAllSystems (system: let
+      pkgs = import nixpkgs {
+        inherit system;
+        config = {
+          android_sdk.accept_license = true;
+          allowUnfree = true;
+        };
+      };
+    in {
+      default = pkgs.mkShell {
+        packages = with pkgs; [
+          (python312.withPackages (
+            ppkgs:
+              with python312Packages; [
+                pip # python package manager
+                fastapi # web framework
+                pandas # data manipulation
+                pydantic # data validation
+                uvicorn # ASGI server
+                sqlalchemy # ORM
+                python-multipart # fastapi multipart form data
+              ]
+          ))
+          fastapi-cli
+          sqlitestudio
+        ];
+      };
+    });
+    # app for backing up the data
+    apps = forAllSystems (system: let
+      pkgs = import nixpkgs {
+        inherit system;
+        config = {
+          android_sdk.accept_license = true;
+          allowUnfree = true;
+        };
+      };
+    in {
+      default = pkgs.fastapi-cli;
+      backup-db = pkgs.writeShellApplication {
+        name = "backup-db";
+        runtimeInputs = [ pkgs.zip ];
+        text = ''
+          # date
+          DATE=$(date +%Y-%m-%d)
+          # backup directory
+          BACKUP_DIR=~/aifred-backup/
+          # create backup directory if it doesn't exist
+          mkdir -p $BACKUP_DIR
+
+          # backup file name
+          BACKUP_FILE=$BACKUP_DIR/backup-$DATE.zip
+          zip -r $BACKUP_FILE data/
+
+          # move backup file to backup directory
+          mv #BACKUP_FILE $BACKUP_DIR
+        '';
+      };
+    });
+  };
+}