Add auto-restart watch mode for telegram bridge dev command

[geier]

Context

The Telegram bridge entrypoint (docker/telegram-bridge.ts) is often run manually during local development (for example bun run docker/telegram-bridge.ts).

Right now, code edits require manually stopping and re-running the process, which slows iteration when working on Telegram flow logic.

Goal

Make the local Telegram bridge run workflow auto-restart on source changes.

Proposed direction

• Prefer Bun-native watch mode (for example bun --watch docker/telegram-bridge.ts) so no extra dependency is needed.
• Provide a stable developer command (script/alias/doc pattern) so contributors use one canonical command instead of remembering runtime flags.

Files to update (likely)

• README.md (Telegram bridge dev instructions)
• docker/README.md (optional, if bridge run instructions are documented there)
• Optional command definition location if adding a reusable script target (repo-level if available)

Acceptance Criteria

• A documented command exists for running the Telegram bridge with auto-restart on file changes.
• The command restarts the process when either docker/telegram-bridge.ts or shared/telegram-bridge.ts is edited.
• Existing non-watch/production invocation paths (e.g. s6 service and Docker runtime) remain unchanged.
• Docs clearly distinguish local watch-mode usage from production container execution.