fix(ha-bootstrap): priority staggering and candidate_id in election

Two Raft correctness fixes:

1. Priority staggering in ha_wait_for_heartbeat_or_timeout():
   Add my_priority × election_priority_step_ms to the timeout so
   ctrl-a (priority=0) times out first and starts election before
   ctrl-b (priority=1) and ctrl-c (priority=2). This gives the
   highest-priority node a head start and prevents simultaneous
   campaigning that causes perpetual split votes.

2. candidate_id in vote RPC:
   Pass the actual node name (myconf->name) as candidate_id instead
   of "". This fixes the voted_for deduplication gate (Req 2.6):
   a peer that already voted for ctrl-a will correctly deny a
   second vote request from ctrl-b in the same term.

   Thread context gets my_name field; am_i_primary_quorum() takes
   my_name parameter; all call sites updated (myapp.c, ha.c RDHUP,
   test_ha_election.c stubs).

src/controller/myapp.c

@@ -152,7 +152,8 @@ int myapp_run(myconf_t* myconf)
         uint64_t my_lsn = (uint64_t)atomic_load_explicit(&c.ha.applied_lsn,
                                                           memory_order_acquire);
         ctrl_role_t elected = am_i_primary_quorum(
-            &c.ha, n_peers, (n_other > 0) ? peer_ptrs : NULL, my_tag, my_lsn);
+            &c.ha, n_peers, (n_other > 0) ? peer_ptrs : NULL,
+            my_tag, my_lsn, myconf->name);
 
         if (elected == CTRL_PRIMARY) {
             final_role = CTRL_PRIMARY;