Fix SQL parsing, DBNull handling, and resource leaks

[Copilot]

• [x] Explore repository structure and understand the codebase
• [x] Fix bug: Missing .Trim() in SQL statement check in SqlCeDatabase35.SqlCeDatabase.ExecuteQuery() - queries with leading whitespace were not being recognized as SELECT statements
• [x] Fix bug: DBNull.Value not handled in TableExtensions.GenerateDataScript() - database NULL values were not properly converted to SQL NULL in generated scripts
• [x] Fix bug: Resource leaks in StringEncryptionHelper - all IDisposable objects (MemoryStream, CryptoStream, FileStream, Rijndael, PasswordDeriveBytes) are now properly disposed using using statements
• [x] Replace redundant cs.Close() calls with cs.FlushFinalBlock() for clarity since using statements handle disposal

Original prompt

Find and resolve bugs and issue in the current code base. Be as thorough as possible

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[christianhelle]

@copilot apply changes based on the comments in this thread

[Copilot]

@copilot apply changes based on the comments in this thread

Applied the changes - replaced redundant cs.Close() calls with cs.FlushFinalBlock() in both encrypt and decrypt byte array methods (commit 1bba89d). The using statements now handle disposal while FlushFinalBlock() explicitly finalizes the cryptographic operations.

Note: The obsolete GetBytes method warnings are pre-existing in the codebase. Updating PasswordDeriveBytes to a modern alternative like Rfc2898DeriveBytes would be a breaking change that could affect existing encrypted passwords, so I've left those as-is.