ci: exclude PostgreSQL tests from CI workflow

- Added --exclude-group=backend-db flag to test command in Gitea workflow
- Marked all PostgreSQL-dependent tests with ->group('backend-db')
- Tests in BackendModelsTest.php (8 tests) now excluded from CI
- Tests in SyncBackendDataPoolTest.php (8 tests) now excluded from CI
- These tests still run locally where PostgreSQL backend is available

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

tests/Feature/BackendModelsTest.php

@@ -9,7 +9,7 @@ test('can connect to backend schema', function () {
     $count = Transaction::count();
 
     expect($count)->toBeGreaterThanOrEqual(0);
-});
+})->group('backend-db');
 
 test('can read transactions from backend schema', function () {
     $transaction = Transaction::first();
@@ -22,7 +22,7 @@ test('can read transactions from backend schema', function () {
     } else {
         expect(true)->toBeTrue(); // No transactions yet
     }
-});
+})->group('backend-db');
 
 test('can read transaction outputs', function () {
     $output = TransactionOutput::first();
@@ -35,7 +35,7 @@ test('can read transaction outputs', function () {
     } else {
         expect(true)->toBeTrue(); // No outputs yet
     }
-});
+})->group('backend-db');
 
 test('transaction has outputs relationship', function () {
     $transaction = Transaction::with('outputs')->first();
@@ -45,7 +45,7 @@ test('transaction has outputs relationship', function () {
     } else {
         expect(true)->toBeTrue(); // No transactions yet
     }
-});
+})->group('backend-db');
 
 test('can get specific output by key', function () {
     $transaction = Transaction::with('outputs')->first();
@@ -58,7 +58,7 @@ test('can get specific output by key', function () {
     } else {
         expect(true)->toBeTrue(); // No transactions with outputs yet
     }
-});
+})->group('backend-db');
 
 test('can get company info from transaction', function () {
     $transaction = Transaction::with('outputs')->first();
@@ -71,7 +71,7 @@ test('can get company info from transaction', function () {
     } else {
         expect(true)->toBeTrue();
     }
-});
+})->group('backend-db');
 
 test('can get risk assessment from transaction', function () {
     $transaction = Transaction::with('outputs')->first();
@@ -88,7 +88,7 @@ test('can get risk assessment from transaction', function () {
     } else {
         expect(true)->toBeTrue();
     }
-});
+})->group('backend-db');
 
 test('can check if transaction requires review', function () {
     $transaction = Transaction::with('outputs')->first();
@@ -100,7 +100,7 @@ test('can check if transaction requires review', function () {
     } else {
         expect(true)->toBeTrue();
     }
-});
+})->group('backend-db');
 
 test('transaction output keys constants exist', function () {
     expect(TransactionOutput::KEY_COMPANY_INFO)->toBe('company_info');