chore: hide private ssh key when on edit polydock store page

[dan2k3k4]

Improves the security by moving the storage of the lagoon_deploy_private_key from a plain text column in the polydock_stores table to an encrypted value in the polydock_variables table

Changes:

• Added 2026_02_05_133703_move_lagoon_deploy_private_key_to_variables.php to migrate existing keys to the polydock_variables table with encryption and drop the lagoon_deploy_private_key column from polydock_stores
• Updated App\Models\PolydockStore to remove lagoon_deploy_private_key from $fillable
• Added an accessor getLagoonDeployPrivateKeyAttribute to seamlessly retrieve the decrypted key from the variables relation, ensuring backward compatibility
• Updated App\Console\Commands\CreateStore to store the private key using setPolydockVariableValue with encrypted => true
• Updated CreatePolydockStore and EditPolydockStore pages to handle the lagoon_deploy_private_key field manually. The key is now intercepted during creation/update and stored securely via the variable helper, rather than being saved directly to the model.
• Updated DatabaseSeeder, AmazeeTrialSeeder, and LocalstackSeeder to use the secure storage method for creating stores with deploy keys
• Added getPublicKeyFromPrivateKey helper in LagoonHelper to support key derivation for display in the UI.

Security Implications:

• The private SSH key used for Lagoon deployments is no longer stored in plain text in the main stores table.
• It is now encrypted at rest using Laravel's Crypt facade within the polydock_variables table.

Backward Compatibility:

• The getLagoonDeployPrivateKeyAttribute accessor ensures that any existing code accessing $store->lagoon_deploy_private_key continues to work without modification, automatically fetching and decrypting the value.