Suggest saving new credentials after login when entry is not found in database (MagicKeyboard / Autofill)

### Checks - [x] I have read the Wiki, searched the open issues, and still think this is a new feature. ### Explain the problem clearly and succinctly: When using MagicKeyboard or Autofill, KeePassDX already prompts the user to unlock the database and then shows a list of saved entries matching the current app/website. However, if no matching entry is found, nothing happens the user is simply shown an empty list or no suggestion at all. This means that if a user logs into an app/website with credentials that are **not yet saved** in their KeePass database, KeePassDX offers no way to proactively capture and save those credentials. The user must manually open KeePassDX and create a new entry, which is a friction-heavy workflow compared to native password managers (Google Password, Samsung Pass, etc.) and browser-based KeePass extensions (KeePassXC-Browser, etc.). ### Describe the solution you'd like: The proposed flow would be: 1. User accesses a login screen on any app/website. 2. KeePassDX (MagicKeyboard or Autofill service) checks the database for a matching entry. 3. If **no match is found** and the user proceeds to log in (or after a login is detected), KeePassDX shows a prompt: **"Save credentials to KeePassDX?"** 4. The user can confirm, and a new entry is pre-filled with: - The app package name / website URL (already collected by the autofill/keyboard context) - Username field value - Password field value 5. The user can edit details and confirm saving the entry directly into their database. This logic is already partially in place: KeePassDX already knows **which app is being accessed** (it uses this to filter entries), and it already knows **whether an entry exists or not**. The missing step is simply offering to save when no entry is found. This behavior mirrors what is already implemented in: - Google Password Manager - Samsung Pass - KeePassXC-Browser extension (desktop) - Safe In Cloud - Zoho Vault ### Describe alternatives you've considered: The current workaround is to manually open KeePassDX, navigate to the correct group, and create a new entry by hand, filling in the URL, username, and password manually. This works but is tedious and error-prone, especially for users who rely on KeePassDX as their primary password manager on Android. Another workaround mentioned in issue #1779 is using the MagicKeyboard "Add entry" button, which pre-fills the app package name. However, this still requires the user to manually initiate the action and does not capture the credentials already typed in the login form. ### Additional context: This feature is particularly relevant now that KeePassDX supports both MagicKeyboard and Autofill service. Since the app already detects the current app/website context and queries the database for matching entries, the infrastructure to support this "save new credential" prompt is largely already in place. Related issues: - #1779 (Painful process of sign-up with keepass into any website/app, should be enhanced) - #1216 (improve save credential flow - closed) This is a distinct request from #1779 (which focuses on sign-up UX) and #1216 (which focuses on the flow after the save action). This issue specifically requests **proactive detection of unsaved credentials at login time** and a prompt to save them. The two scenarios where this prompt should appear are: 1. **New credentials**: the app/website has no matching entry at all in the database → offer to **save** a new entry. 2. **Updated credentials**: the app/website has a matching entry, but the username or password used differs from what is saved → offer to **update** the existing entry. This dual behavior (save + update) is standard across all major password managers: - **Zoho Vault** (Android app) - **Safe in Cloud** (Android app) - **Google Password Manager** (Android / Chrome) - **Microsoft Edge / Authenticator** password manager - **Firefox** built-in password manager - **Bitwarden**, **1Password**, **KeePassXC-Browser** (browser extensions) All of these prompt the user after a login form is submitted, covering both the "new entry" and "update existing entry" cases.