Fixes #13327

Summary

• Close the modal database unlock dialog when its target database is unlocked through another path.
• Keep the unlock dialog target list in DatabaseTabWidget so the dialog can still be completed if its internal state was cleared during the external unlock.
• Complete pending Secret Service unlock requests immediately if the database is already unlocked when the dialog reports success.

Testing

• Built KeePassXC with CMake/Ninja: cmake --build build-rel
• Manually reproduced on KDE/Wayland with KeePassXC as Secret Service and an external MainWindow D-Bus unlock helper.
• Verified the database unlocks and the stale unlock dialog closes after the external unlock.

AI Assistance

This patch was developed with assistance from OpenAI Codex, based on GPT-5.5. The final code was manually reviewed, built, and tested on the affected system.