feat: login rate limiting, network drivers in initfs

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.

local/patches/base/P4-initfs-network-services.patch

@@ -0,0 +1,24 @@
+--- a/init.initfs.d/60_smolnetd.service	1970-01-01 00:00:00.000000000 +0000
++++ b/init.initfs.d/60_smolnetd.service	2026-05-03 09:49:05.837127632 +0100
+@@ -0,0 +1,7 @@
++[unit]
++description = "Network Stack"
++requires_weak = ["40_drivers.target"]
++
++[service]
++cmd = "smolnetd"
++type = "notify"
+--- a/init.initfs.d/61_dhcpd.service	1970-01-01 00:00:00.000000000 +0000
++++ b/init.initfs.d/61_dhcpd.service	2026-05-03 09:49:05.837757425 +0100
+@@ -0,0 +1,7 @@
++[unit]
++description = "DHCP Client"
++requires_weak = ["60_smolnetd.service"]
++
++[service]
++cmd = "dhcpd"
++type = "oneshot_async"
+--- a/init.initfs.d/.gitkeep	2026-05-03 09:49:05.835495601 +0100
++++ b/init.initfs.d/.gitkeep	1970-01-01 00:00:00.000000000 +0000
+@@ -1 +0,0 @@
+-