feat(pass-extension): add autofill keyboard shortcut command

[yuribodo]

Summary

Adds a keyboard shortcut to trigger autofill in the Proton Pass browser extension, as discussed and approved in #453.

• Registers a new autofill command in Chrome and Firefox manifests with Ctrl+Shift+U as the default shortcut
• Handles the command in the background script by sending an AUTOFILL_TRIGGER message to the active tab's content script
• Content script finds the first detected login field and opens the autofill dropdown, reusing the existing inline dropdown flow

Closes #453

Changes

File	Change
manifest-chrome.json	Added "autofill" command entry
manifest-firefox.json	Added "autofill" command entry
src/types/messages.ts	Added AUTOFILL_TRIGGER to WorkerMessageType enum
src/lib/extension/commands.ts	Added async handler for the "autofill" command
src/lib/extension/commands.spec.ts	Added 4 unit tests for command handling
src/app/content/services/autofill/autofill.service.ts	Registered AUTOFILL_TRIGGER handler using withContext pattern

How it works

1. User presses Ctrl+Shift+U
2. browser.commands.onCommand fires in the background script
3. Background queries the active tab and sends AUTOFILL_TRIGGER via browser.tabs.sendMessage
4. Content script's FrameMessageBroker receives the message
5. Handler finds the first field with DropdownAction.AUTOFILL_LOGIN via formManager.getFields()
6. Opens the autofill dropdown on that field using inline.dropdown.toggle()
7. User selects credentials → normal autofill flow proceeds

If no login field is detected on the page, the shortcut is a no-op.

Design decisions

Default shortcut Ctrl+Shift+U: Chosen to avoid conflicts with existing commands (Ctrl+Shift+X for popup, Ctrl+Shift+L for larger window). The industry standard for autofill is Ctrl+Shift+L (used by Bitwarden and LastPass). If the team is open to it, reassigning Ctrl+Shift+L from open-larger-window to autofill in a follow-up would align with user expectations from competing password managers.

Dropdown approach (not direct autofill): Opens the dropdown instead of auto-filling the top match. This is safer, gives the user control when multiple credentials match, and reuses the existing dropdown infrastructure with minimal new code.

Safari excluded: Safari does not support the browser.commands API. The command listener is already gated by BUILD_TARGET !== 'safari' in worker/index.ts.

Test plan

• Unit tests for handleExtensionCommand (4 tests passing):
  • Opens larger window for open-larger-window command
  • Sends AUTOFILL_TRIGGER to active tab for autofill command
  • Does not send message when no active tab is found
  • Does nothing for unknown commands
• Manual: press Ctrl+Shift+U on a login page → dropdown opens on first login field
• Manual: press Ctrl+Shift+U on a page with no login form → nothing happens
• Manual: verify Ctrl+Shift+X and Ctrl+Shift+L still work as before
• Manual: verify new shortcut appears in Settings → Shortcuts