feat(daemon): add shared cross-process connection registry

The daemon forks one child per accepted connection, so per-module and
per-source accounting must live in state shared across the children. Add a
fixed-size registry carved from an anonymous shared mapping
(mmap(MAP_SHARED|MAP_ANONYMOUS)) created before the accept loop: a slot
lifecycle (FREE/CLAIMED/REGISTERED) with parent claim/reclaim and a
lock-free, open-addressed per-source table for the per-host occupancy and
the shared auth-failure counter. C11 atomics only; no pthread locks across
fork.

Unit tests cover slot exhaustion, the module/host caps, pid reclaim and
fork-shared visibility.

CMakeLists.txt

@@ -86,6 +86,7 @@ set(SHARED_SRCS
 	src/shared/config.c
 	src/shared/credentials.c
 	src/shared/daemon_conf.c
+	src/shared/daemon_limits.c
 	src/shared/data.c
 	src/shared/delay_updates.c
 	src/shared/delta.c
@@ -205,6 +206,7 @@ set(TEST_SRCS
 	tests/test_config.c
 	tests/test_credentials.c
 	tests/test_daemon_conf.c
+	tests/test_daemon_limits.c
 	tests/test_data.c
 	tests/test_delay_updates.c
 	tests/test_delta.c