Add case-insensitive collation settings to SQLite test database

[G3mha]

Describe the bug

Originated during discussion of PR #2854

SQLite test database uses case-sensitive collation while production MySQL uses case-insensitive, causing test failures for case-insensitive string operations.

To Reproduce
Steps to reproduce the behavior:

1. Go to file tests/Feature/Api/V1/UserSummaryTest.php and add the following test case:

public function testUsernameCaseConsistency(): void
{
    $user = User::factory()->create([
        'User' => 'NicoPlaysThings',
    ]);
    $variations = [
        'NICOPLAYSTHINGS',
        'nicoplaysthings',
        'NicoPlaysThings',
    ];

    foreach ($variations as $input) {
        $response = $this->get($this->apiUrl('GetUserSummary', ['u' => $input]));
        $response->assertOk()
                ->assertJsonPath('User', 'NicoPlaysThings')
                ->assertJsonPath('LastActivity.User', 'NicoPlaysThings')
                ->assertJsonPath('UserPic', '/UserPic/NicoPlaysThings.png');
    }
}

2. Run the test involving case-insensitive username lookups:

php artisan test tests/Feature/Api/V1/UserSummaryTest.php --filter testUsernameCaseConsistency

3. Observe test failure due to collation mismatch
4. See PR fix(API_GetUserSummary): handle username case sensitivity and use canonical username #2854 for the complete discussion on this error

Expected behavior

• SQLite test database should use case-insensitive collation matching MySQL's behavior
• Tests should pass regardless of username case variations
• UserSummary API tests should succeed with usernames like 'NICOPLAYSTHINGS', 'nicoplaysthings', 'NicoPlaysThings'

Additional context

• MySQL uses _ci collation by default
• SQLite test environment needs equivalent case-insensitive configuration
• Issue affects test coverage as case-sensitivity tests must be omitted
• Reference PR fix(API_GetUserSummary): handle username case sensitivity and use canonical username #2854 where this caused test coverage gaps
• Environment: PHPUnit test suite using SQLite