Add owner restart command and keep the gateway connection alive

[HiLleywyn]

Summary

• Adds .ai restart / .ai reboot (alias) and a /restart slash command, gated to the bot owner via OWNER_ID or the Discord application owner. The command re-execs the Python interpreter after a graceful shutdown, so a wedged process clears without a redeploy.
• Adds .ai shutdown (also owner only) for clean exits, with a confirmation prompt.
• Hardens the outer loop in main.py so it reconnects on any connection error (not just rate-limits) with exponential backoff up to 60s; backoff resets after a successful login so a healthy bot that drops hours later still comes back quickly.
• Adds a heartbeat watchdog inside ArchimedesBot that force-closes a quiet websocket (no healthy heartbeat for 2 minutes) so discord.py's auto-reconnect always has a chance to kick in. Also logs on_connect / on_resumed / on_disconnect so a future drop leaves a paper trail.

Test plan

• pytest tests/ passes (157 / 157)
• Run .ai restart in a server, watch the process re-exec and the bot come back online
• Confirm /restart slash command appears for the owner only
• Confirm .ai restart from a non-owner is rejected with "Only the bot owner can use this command."
• Disconnect the host network briefly and confirm the outer loop reconnects with backoff (look for Reconnecting in Ns (attempt N) lines)
• Idle the bot long enough to hit the previous drop and confirm the watchdog logs Gateway looks stale ... closing websocket to force reconnect. if the gateway wedges

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