fix(firecracker): launch infra-VM gateway as a module, not /app/gateway_init.py

The infra VM's init boots the orchestrator control plane AND the gateway data
plane (egress/git-http/supervise). Since 5ad3449 moved the daemons into the
installed `bot_bottle` package, there is no `/app/gateway_init.py` file — the
gateway image's entrypoint is `python3 -m bot_bottle.gateway_init`. But the
firecracker init still spawned the old file path, so the guest logged:

    python3: can't open file '/app/gateway_init.py': No such file or directory

The control plane came up (it already used `python3 -m bot_bottle.orchestrator`)
but the gateway never started, so mitmproxy never generated its CA and launch
died with "gateway CA not available after 30s". Mirror the orchestrator line:
run the gateway as `python3 -m bot_bottle.gateway_init` (bot_bottle resolves
from the /app CWD, same as the control plane; egress-entrypoint.sh /
egress_addon.py are present from the gateway base image).

Third build/runtime bug from 5ad3449's package refactor that the Firecracker
integration suite never exercised (the artifact publish was broken, so the
job 404'd before boot). Changes the init, so the infra artifact version moves;
the matching rootfs has been rebuilt and published.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01A9qa3xoavjQScufDfZaXKR

bot_bottle/backend/firecracker/infra_vm.py

@@ -433,7 +433,7 @@ BOT_BOTTLE_ROOT=/var/lib/bot-bottle python3 -m bot_bottle.orchestrator \\
 BOT_BOTTLE_GATEWAY_DAEMONS=egress,git-http,supervise \\
 BOT_BOTTLE_ORCHESTRATOR_URL=http://127.0.0.1:{CONTROL_PLANE_PORT} \\
 SUPERVISE_DB_PATH=/var/lib/bot-bottle/db/bot-bottle.db \\
-    python3 /app/gateway_init.py &
+    python3 -m bot_bottle.gateway_init &
 
 # Reap as PID 1; children are backgrounded, so `wait` blocks.
 while : ; do wait ; done