Update dependencies and project configuration

Add Nix flake support, update .gitignore to ignore SSL certs, upgrade
@types/bun and TypeScript versions, and update frontend SDK URLs in
index.html and sw.js to new API endpoints

flake.nix

@@ -0,0 +1,21 @@
+{
+  description = "DropUI Django";
+
+  inputs.nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";
+
+  outputs = { self, nixpkgs, ... }: let
+    system = "x86_64-linux";
+    pkgs = import nixpkgs {
+      inherit system;
+      config.allowUnfree = true;
+    };
+  in {
+    devShells.${system}.default = pkgs.mkShell {
+      buildInputs = with pkgs; [
+        bun
+        biome
+        google-chrome
+      ];
+    };
+  };
+}