Pipeline step messages and prompts should be localized

## Problem

Pipeline step messages (status text, confirmation prompts, error messages) in the AppHost are all hardcoded string literals. None are in resource files for localization.

This affects all pipeline steps across all compute environments:
- Deploy/publish step messages
- Destroy confirmation prompts
- Azure provisioning messages
- Docker Compose up/down messages
- Helm deploy/uninstall messages
- Parameter prompts (`PromptNotificationAsync` calls)

## Expected behavior

User-facing messages in pipeline steps should be in `.resx` resource files for translation, consistent with how CLI command strings are handled.

## Context

Raised by @JamesNK in #16097. This is a pre-existing pattern — no pipeline prompts are currently localized.