fix(election-iomgr-refactor): config replication and RDHUP failover chain

- cluster.c: fix upgradeConfig handler (standbys apply, not primaries)
- cluster.c: fix raw_pkt_copy opcode peek (read scalar before capn_free)
- config_repl.h: enable CONF_ENABLE_UPGRADE_CONFIG=1
- config_repl.c: use client_ssl_ctx for outgoing config fetch connections
- config_repl.c: after config fetch, run cluster_init_phase2 + find_primary
- join.c: push config to newly-joined standbys on OPCode_join
- myapp.c: schedule fetch_config_from_primary after skipping own election
- ha.c: arm heartbeat timeout watchdog after find_and_connect_to_primary

src/controller/config_repl.h

@@ -16,9 +16,9 @@
 /* Sentinel name for the synthetic lost-and-found queue and host */
 #define XCE_LOST_AND_FOUND_NAME "lost_and_found"
 
-/* Compile-time gate for OP_upgradeConfig (Phase 2, default disabled) */
+/* Compile-time gate for OP_upgradeConfig (enabled: standbys apply pushed config) */
 #ifndef CONF_ENABLE_UPGRADE_CONFIG
-#define CONF_ENABLE_UPGRADE_CONFIG 0
+#define CONF_ENABLE_UPGRADE_CONFIG 1
 #endif
 
 /* Push timeout for standby fan-out (ms) */