Add cover_path column to groups table for group cover photo feature

db/init.sql

@@ -1,7 +1,20 @@
+CREATE TABLE IF NOT EXISTS branches (
+  id SERIAL PRIMARY KEY,
+  name VARCHAR(200) NOT NULL UNIQUE,
+  address TEXT,
+  phone VARCHAR(50),
+  created_at TIMESTAMPTZ DEFAULT now()
+);
+
 CREATE TABLE IF NOT EXISTS groups (
   id SERIAL PRIMARY KEY,
   name VARCHAR(100) NOT NULL UNIQUE,
-  created_at TIMESTAMPTZ DEFAULT now()
+  branch_id INT REFERENCES branches(id) ON DELETE SET NULL,
+  created_at TIMESTAMPTZ DEFAULT now(),
+  day_of_week INT,
+  time_start TIME,
+  time_end TIME,
+  cover_path VARCHAR(255)
 );
 
 CREATE TABLE IF NOT EXISTS students (
@@ -72,8 +85,36 @@ CREATE TABLE IF NOT EXISTS project_files (
   detached_at TIMESTAMPTZ
 );
 
+CREATE TABLE IF NOT EXISTS users (
+  id SERIAL PRIMARY KEY,
+  username VARCHAR(100) NOT NULL UNIQUE,
+  password_hash VARCHAR(255) NOT NULL,
+  name VARCHAR(150),
+  role VARCHAR(20) NOT NULL DEFAULT 'tutor' CHECK (role IN ('admin','tutor')),
+  is_active BOOLEAN DEFAULT true,
+  created_at TIMESTAMPTZ DEFAULT now()
+);
+
+CREATE TABLE IF NOT EXISTS user_branches (
+  user_id INT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+  branch_id INT NOT NULL REFERENCES branches(id) ON DELETE CASCADE,
+  PRIMARY KEY (user_id, branch_id)
+);
+
+CREATE TABLE IF NOT EXISTS sessions (
+  id SERIAL PRIMARY KEY,
+  user_id INT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+  token VARCHAR(64) NOT NULL UNIQUE,
+  created_at TIMESTAMPTZ DEFAULT now(),
+  expires_at TIMESTAMPTZ NOT NULL
+);
+
+CREATE INDEX IF NOT EXISTS idx_sessions_token ON sessions(token);
+CREATE INDEX IF NOT EXISTS idx_sessions_expires_at ON sessions(expires_at);
+
 CREATE TABLE IF NOT EXISTS audit_log (
   id SERIAL PRIMARY KEY,
+  user_id INT REFERENCES users(id) ON DELETE SET NULL,
   action VARCHAR(100) NOT NULL,
   target JSONB,
   ip VARCHAR(45),