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/join.c

@@ -5,6 +5,7 @@
 #include <unistd.h>
 
 #include "cluster.h"
+#include "config_repl.h"
 #include "ha.h"
 #include "xce/cluster_def.h"
 #include "xce/errnox.h"
@@ -163,6 +164,11 @@ static int handle_controller_join(cluster_t* c, endpoint_t* ep,
         INFO("controller %s joined — %d standby(s) tracked",
              request->from ? request->from->name : "?",
              c->ha.standby_endpoints->count);
+
+        /* Immediately push current config to the newly-joined standby so it
+         * doesn't have to wait for the next scheduled push. */
+        if (ha_is_primary(&c->ha))
+            push_config_to_standbys(c, NULL, 0, NULL, 0);
     }
 
     return 0;