feat(payment): implement database-driven payment provider system with encrypted configuration support

- Add PaymentProviderSeeder with initial provider data (Stripe, Lemon Squeezy, Polar, OxaPay, Crypto, Activation Key)
  - Create migration to disable JSON constraints and change configuration column from JSON to TEXT
  - Update PaymentProvider model cast from 'array' to 'encrypted:array' for secure configuration storage

database/migrations/2025_12_03_102201_change_configuration_column_to_text_in_payment_providers_table.php

@@ -0,0 +1,70 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+use Illuminate\Support\Facades\DB;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        // Detect DB driver
+        $driver = Schema::getConnection()->getDriverName();
+
+        // --- MySQL / MariaDB only ---
+        // Drop JSON check constraints if they exist (safely)
+        if (in_array($driver, ['mysql', 'mariadb'])) {
+            try {
+                // MySQL automatically names check constraints in different ways,
+                // so we attempt a generic drop and ignore failures.
+                DB::statement("ALTER TABLE `payment_providers` DROP CHECK `payment_providers.configuration`;");
+            } catch (\Throwable $e) {
+                // ignore if constraint does not exist
+            }
+        }
+
+        // --- PostgreSQL ---
+        // PostgreSQL may also require dropping check constraints but constraint names are random.
+        // We try to drop any constraint *that checks JSON*.
+        if ($driver === 'pgsql') {
+            try {
+                $constraint = DB::selectOne("
+                    SELECT conname
+                    FROM pg_constraint
+                    JOIN pg_class ON pg_constraint.conrelid = pg_class.oid
+                    WHERE relname = 'payment_providers'
+                    AND pg_get_constraintdef(pg_constraint.oid) LIKE '%configuration%json%';
+                ");
+
+                if (!empty($constraint->conname)) {
+                    DB::statement("ALTER TABLE payment_providers DROP CONSTRAINT {$constraint->conname};");
+                }
+            } catch (\Throwable $e) {
+                // ignore if constraint does not exist
+            }
+        }
+
+        // --- SQLite & SQL Server ---
+        // No action needed:
+        // SQLite doesn’t enforce JSON CHECK constraints
+        // SQL Server does not create JSON CHECK constraints automatically.
+
+        Schema::table('payment_providers', function (Blueprint $table) {
+            // Replace JSON type with LONGTEXT / TEXT depending on driver
+            // Laravel automatically maps this properly for each database.
+            $table->longText('configuration')->change();
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('payment_providers', function (Blueprint $table) {
+            // revert to JSON column
+            // Laravel maps this to appropriate driver types
+            $table->json('configuration')->change();
+        });
+
+        // Optionally: you can restore JSON CHECK constraints here, but it's not required
+    }
+};