fix(backup): validate MongoDB collection names in backup input

Add validateDatabasesBackupInput() helper that properly parses all
database backup formats including MongoDB's "db:col1,col2|db2:col3"
and validates each component individually.

- Validate and escape collection names in DatabaseBackupJob
- Replace comma-only split in BackupEdit with format-aware validation
- Add input validation in API create_backup and update_backup endpoints
- Add unit tests for collection name and multi-format validation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/Unit/DatabaseBackupSecurityTest.php

@@ -81,3 +81,64 @@ test('database backup accepts legitimate database names', function () {
     expect(fn () => validateShellSafePath('test123', 'database name'))
         ->not->toThrow(Exception::class);
 });
+
+// --- MongoDB collection name validation tests ---
+
+test('mongodb collection name rejects command substitution injection', function () {
+    expect(fn () => validateShellSafePath('$(touch /tmp/pwned)', 'collection name'))
+        ->toThrow(Exception::class);
+});
+
+test('mongodb collection name rejects backtick injection', function () {
+    expect(fn () => validateShellSafePath('`id > /tmp/pwned`', 'collection name'))
+        ->toThrow(Exception::class);
+});
+
+test('mongodb collection name rejects semicolon injection', function () {
+    expect(fn () => validateShellSafePath('col1; rm -rf /', 'collection name'))
+        ->toThrow(Exception::class);
+});
+
+test('mongodb collection name rejects ampersand injection', function () {
+    expect(fn () => validateShellSafePath('col1 & whoami', 'collection name'))
+        ->toThrow(Exception::class);
+});
+
+test('mongodb collection name rejects redirect injection', function () {
+    expect(fn () => validateShellSafePath('col1 > /tmp/pwned', 'collection name'))
+        ->toThrow(Exception::class);
+});
+
+test('validateDatabasesBackupInput validates mongodb format with collection names', function () {
+    // Valid MongoDB formats should pass
+    expect(fn () => validateDatabasesBackupInput('mydb'))
+        ->not->toThrow(Exception::class);
+
+    expect(fn () => validateDatabasesBackupInput('mydb:col1,col2'))
+        ->not->toThrow(Exception::class);
+
+    expect(fn () => validateDatabasesBackupInput('db1:col1,col2|db2:col3'))
+        ->not->toThrow(Exception::class);
+
+    expect(fn () => validateDatabasesBackupInput('all'))
+        ->not->toThrow(Exception::class);
+});
+
+test('validateDatabasesBackupInput rejects injection in collection names', function () {
+    // Command substitution in collection name
+    expect(fn () => validateDatabasesBackupInput('mydb:$(touch /tmp/pwned)'))
+        ->toThrow(Exception::class);
+
+    // Backtick injection in collection name
+    expect(fn () => validateDatabasesBackupInput('mydb:`id`'))
+        ->toThrow(Exception::class);
+
+    // Semicolon in collection name
+    expect(fn () => validateDatabasesBackupInput('mydb:col1;rm -rf /'))
+        ->toThrow(Exception::class);
+});
+
+test('validateDatabasesBackupInput rejects injection in database name within mongo format', function () {
+    expect(fn () => validateDatabasesBackupInput('$(whoami):col1,col2'))
+        ->toThrow(Exception::class);
+});