Add Quick Messages feature

[mcintyre94]

Summary

• QuickMessage SwiftData model — stores text and createdAt, registered in the app's model container
• Quick Messages settings screen — full CRUD list at Settings → Quick Messages, with swipe-to-delete, context menu (Edit/Delete), and an add/edit sheet
• Quick Messages picker in chat — accessible via the attachment menu (+ button); tapping a message appends it to the current input (with a newline separator if there's existing text), so you can edit before sending

Test plan

• Settings → Quick Messages shows empty state with prompt to add
• Tap + to add a new message; Save persists it, Cancel discards
• Tap an existing message to edit it; changes persist on Save
• Swipe to delete and long-press context menu both offer Delete
• In chat, tap + → Quick Messages to open the picker
• Selecting a message appends to an empty input; appends with newline to non-empty input
• Picker shows empty state if no messages have been created
• Works on iPhone (compact) and iPad/Mac (regular)

🤖 Generated with Claude Code

[claude]

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.