✨feature: Update database schema to separate payees from payments

includes/db.php

@@ -3,15 +3,22 @@ class DB {
   public static function connect() {
     $db = new PDO('sqlite:'.__DIR__.'/../data/bills.db');
 
+    $db->exec("CREATE TABLE IF NOT EXISTS payees (
+      id INTEGER PRIMARY KEY AUTOINCREMENT,
+      name TEXT NOT NULL UNIQUE,
+      createdAt TEXT DEFAULT CURRENT_TIMESTAMP
+    )");
+
     $db->exec("CREATE TABLE IF NOT EXISTS bills (
-        id INTEGER PRIMARY KEY,
-        billDate TEXT NOT NULL,
-        billName TEXT NOT NULL,
-        amount REAL NOT NULL,
-        paymentId TEXT,
-        year INTEGER NOT NULL,
-        comment TEXT
-      )");
+      id INTEGER PRIMARY KEY AUTOINCREMENT,
+      billDate TEXT NOT NULL,
+      payeeId INTEGER NOT NULL,
+      amount REAL NOT NULL,
+      paymentId TEXT,
+      comment TEXT,
+      year INTEGER NOT NULL,
+      FOREIGN KEY (payeeId) REFERENCES payees(id) ON DELETE CASCADE
+    )");
 
     return $db;
   }