Fix flake.nix: node 22, shebang indentation, databaseUrl default, assertion

- Upgrade to nodejs_22 (22.22.2) for better Vite 6 compatibility
- Fix wrapper script shebang broken by heredoc indentation
- Add preBuild step for svelte-kit sync
- Default databaseUrl to "" so environmentFile-only configs don't fail eval
- Add assertion ensuring either databaseUrl or environmentFile is set

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

flake.nix

@@ -10,7 +10,7 @@
     flake-utils.lib.eachDefaultSystem (system:
       let
         pkgs = import nixpkgs { inherit system; };
-        nodejs = pkgs.nodejs_20;
+        nodejs = pkgs.nodejs_22;
       in
       {
         # Development shell: `nix develop`
@@ -38,19 +38,26 @@
 
           src = ./.;
 
-          npmDepsHash = "";  # Run `nix build` once to get the correct hash
+          npmDepsHash = "";  # Run `nix build` once — it will fail and print the correct hash
+
+          nodejs = pkgs.nodejs_22;
 
           nativeBuildInputs = [
             pkgs.pkg-config
-            pkgs.python3 # needed by some native modules
+            pkgs.python3 # needed by sharp native rebuild
           ];
 
           buildInputs = [
-            pkgs.vips     # sharp
+            pkgs.vips
             pkgs.glib
             pkgs.expat
           ];
 
+          # SvelteKit needs sync before build
+          preBuild = ''
+            npx svelte-kit sync
+          '';
+
           npmBuildScript = "build";
 
           installPhase = ''
@@ -62,10 +69,10 @@
             cp package.json $out/lib/buildfor_life_repair/
 
             mkdir -p $out/bin
-            cat > $out/bin/buildfor_life_repair <<EOF
+            cat > $out/bin/buildfor_life_repair <<'WRAPPER'
 #!/usr/bin/env bash
-            exec ${nodejs}/bin/node $out/lib/buildfor_life_repair/index.js "\$@"
-            EOF
+exec ${pkgs.nodejs_22}/bin/node $out/lib/buildfor_life_repair/index.js "$@"
+WRAPPER
             chmod +x $out/bin/buildfor_life_repair
 
             runHook postInstall
@@ -102,14 +109,15 @@
 
             databaseUrl = lib.mkOption {
               type = lib.types.str;
-              description = "PostgreSQL connection string";
+              default = "";
+              description = "PostgreSQL connection string. Leave empty if using environmentFile.";
               example = "postgresql://bflr:password@localhost:5432/buildfor_life_repair";
             };
 
             environmentFile = lib.mkOption {
               type = lib.types.nullOr lib.types.path;
               default = null;
-              description = "Path to environment file with secrets (DATABASE_URL, etc). Overrides databaseUrl if set.";
+              description = "Path to environment file with secrets (DATABASE_URL, etc). Takes precedence over databaseUrl.";
             };
 
             baseUrl = lib.mkOption {
@@ -144,6 +152,13 @@
           };
 
           config = lib.mkIf cfg.enable {
+            assertions = [
+              {
+                assertion = cfg.databaseUrl != "" || cfg.environmentFile != null;
+                message = "services.buildfor-life-repair: Either databaseUrl or environmentFile must be set.";
+              }
+            ];
+
             users.users.${cfg.user} = {
               isSystemUser = true;
               group = cfg.group;
@@ -164,7 +179,7 @@
                 HOST = cfg.host;
                 BASE_URL = cfg.baseUrl;
                 UPLOAD_DIR = cfg.uploadDir;
-              } // lib.optionalAttrs (cfg.environmentFile == null) {
+              } // lib.optionalAttrs (cfg.databaseUrl != "") {
                 DATABASE_URL = cfg.databaseUrl;
               };