feat: add @-mention tagging to notification inline replies

[barrydeen]

Summary

• Add @-mention user tagging popup to notification inline reply composers (both DM and note replies), matching the existing behavior in the note composer
• Add client tag (["client", "Wisp"]) to quick replies sent from the notifications screen when the setting is enabled
• Mention display names are resolved and rendered inline via MentionOutputTransformation

Test plan

• Expand a reply notification, type @ in the inline reply — verify mention popup appears with contacts
• Select a mention candidate — verify nostr:nprofile1... is inserted and rendered as @displayName
• Expand a DM notification, type @ in the inline reply — verify same mention popup behavior
• Send a quick reply from notifications — verify the published event includes ["client", "Wisp"] tag (when enabled in settings)
• Verify emoji shortcode autocomplete still works and is suppressed while mention popup is active