v1.1.7: deep security & reliability audit — 33 bugs fixed

Critical (5):
- Reject empty JWT secret when authEnabled (server.nim)
- Fix 2PC marking uncontacted participants as prepared/committed (disttxn.nim)
- Fix Raft commit index calculation for even-sized clusters (raft.nim)
- Fix REP/DISTTXN protocol auth bypass (server.nim)
- Fix HTTP backup/restore path traversal (httpserver.nim)

High (11):
- Fix WAL write race with flush (lsm.nim)
- Fix MVCC savepoint/rollback deep-copy writeSet (mvcc.nim)
- Fix table mutation during deadlock iteration (mvcc.nim)
- Fix LIMIT 0 returning all rows (executor.nim)
- Fix COUNT(col) counting NULL values — 3 locations (executor.nim)
- Fix EXISTS subquery lowering missing subqueryPlan (executor.nim)
- Fix Raft appendEntries/applyCommitted array vs logical index (raft.nim)
- Fix timing attacks on constantTimeCompare and SCRAM (auth.nim, scram.nim)
- Fix B-tree leaf merge phantom separator key (btree.nim)
- Fix SSL verifyPeer not applied to newContext (ssl.nim)
- Fix sharding connectWithTimeout missing SO_ERROR check (sharding.nim)
- Fix sync replication returning success on partial ack (replication.nim)
- Fix WebSocket JWT expiration not validated (websocket.nim)

Medium (13):
- Fix writeSSTable partial file → tmp + atomic rename (lsm.nim)
- Fix multi-CTE table loss (executor.nim)
- Fix nl_to_sql DML restricted to superuser (executor.nim)
- Fix unbounded plan cache — max 10000 (adaptive.nim)
- Fix migration lock crash persistence — timestamp + stale detection (executor.nim)
- Fix admin panel auth (httpserver.nim)
- Fix MVCC unbounded txn tracking — prune in compactVersions (mvcc.nim)
- Fix connection pool maxLifetime check (pool.nim)
- Fix JWT JSON parser backslash escapes (auth.nim)
- Fix substr(s, start) returning single char (udf.nim)
- Fix loadSSTable minimum file-size check (lsm.nim)
- Fix compaction mmap leak (compaction.nim)
- Fix JSON injection in hybrid_search_filtered (executor.nim)

Low (4):
- Raft loadState logs error instead of silent discard
- Replication healthCheck double-close fixed
- Lexer readIdent double column counting fixed
- WebSocket frame 32-bit overflow guard

All 448 tests passing, 0 failures. Bump version to 1.1.7.

src/barabadb/core/replication.nim

@@ -150,8 +150,9 @@ proc writeLsn*(rm: ReplicationManager, data: seq[byte]): uint64 =
         rm.pendingAcks.del(lsn)
     release(rm.lock)
     if replicasToShip.len > 0 and ackCount < replicasToShip.len:
-      when defined(debug):
-        echo "Replication sync: only ", ackCount, "/", replicasToShip.len, " replicas acked for LSN ", lsn
+      # Sync replication requires ALL replicas to ack — fail if any missed
+      echo "[ERROR] Sync replication failed: only ", ackCount, "/", replicasToShip.len, " replicas acked for LSN ", lsn
+      return 0  # Indicate failure to satisfy sync replication guarantee
     return lsn
   of rmSemiSync:
     if replicasToShip.len > 0:
@@ -259,7 +260,6 @@ proc healthCheck*(rm: ReplicationManager) =
       if not connectWithTimeout(sock, replica.host, Port(replica.port), 1000):
         connected = false
       else:
-        defer: sock.close()
         sock.send("PING\n")
         var response = ""
         try:
@@ -271,7 +271,7 @@ proc healthCheck*(rm: ReplicationManager) =
     except:
       connected = false
     finally:
-      sock.close()
+      try: sock.close() except: discard
 
     if not connected:
       acquire(rm.lock)