Add postgreSQL initiation scripts to flake.nix

.gitignore

@@ -3,3 +3,4 @@ main
 tmp/
 build-errors.log
 result
+.devdata/

flake.nix

@@ -12,7 +12,7 @@
       system:
       let
         pkgs = import nixpkgs { inherit system; };
-        go = pkgs.go_1_24;
+        go = pkgs.go_1_27;
       in
       {
         packages.default = pkgs.buildGoModule {
@@ -60,6 +60,22 @@
 
           shellHook = ''
             echo "go-backend dev shell — $(go version)"
+
+            export PGDATA="$PWD/.devdata/pgdata"
+            export PGHOST="$PWD/.devdata/pgsocket"
+
+            mkdir -p "$PGHOST"
+
+            if [ ! -d "$PGDATA" ]; then
+              echo "Initializing Postgres data dir..."
+              initdb --auth=trust --no-locale --encoding=UTF8 -U postgres >/dev/null
+            fi
+
+            pg_ctl status >/dev/null 2>&1 || pg_ctl start -l "$PWD/.devdata/pg.log" -o "-k $PGHOST -h 127.0.0.1 -p 5432"
+
+            createdb -U postgres -h 127.0.0.1 backend_template 2>/dev/null || true
+
+            alias pg_stop="pg_ctl stop"
           '';
         };