chore: restructure project into backend and frontend folders

- Move all frontend code to frontend/ directory
- Add backend/ with Go project structure (cmd, internal, pkg)
- Add docker-compose.yml for orchestration

backend/internal/db/migrations/000001_create_deliveries_table.down.sql

@@ -0,0 +1 @@
+DROP TABLE IF EXISTS deliveries;

backend/internal/db/migrations/000001_create_deliveries_table.up.sql

@@ -0,0 +1,14 @@
+CREATE TABLE deliveries (
+    id uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+    date date NOT NULL,                          -- хранить как date, отдавать как DD-MM-YYYY
+    pickup_location varchar(20) NOT NULL,        -- warehouse|symbat|nursaya|galaktika
+    product_name text NOT NULL,
+    address text NOT NULL,
+    phone varchar(30) NOT NULL,
+    additional_phone varchar(30),
+    has_elevator boolean NOT NULL DEFAULT false,
+    comment text,
+    status varchar(20) NOT NULL DEFAULT 'new',  -- new|delivered
+    created_at timestamptz DEFAULT now(),
+    updated_at timestamptz DEFAULT now()
+);

backend/internal/db/migrations/000002_create_users_table.down.sql

@@ -0,0 +1 @@
+DROP TABLE IF EXISTS users;

backend/internal/db/migrations/000002_create_users_table.up.sql

@@ -0,0 +1,6 @@
+CREATE TABLE users (
+    id uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+    username VARCHAR(50) NOT NULL UNIQUE,
+    password_hash VARCHAR(255) NOT NULL,
+    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+);