P2-2: Login rate limiting (userutils/login.rs):
- Tracks consecutive failures, resets on success
- 3+ failures: exponential delay up to 30 seconds
- Applies to both password and blank-password login paths
P2-3: Network stack in initfs (base-initfs + service files):
- Added e1000d, rtl8168d to base-initfs BINS
- 60_smolnetd.service: network stack in initfs
- 61_dhcpd.service: DHCP client in initfs
- Network available before switch_root
Part of COMPREHENSIVE-FIX-AND-IMPROVEMENT-PLAN Phases P2.
