Fix duplicate leaderboard entries, add /version command, fix jail DNS

- db/db.go: Add write-time username sync in AddLog to prevent duplicate

  leaderboard entries when users change display names. Revert correlated

  subqueries back to GROUP BY user_id, username (simpler approach).

- db/db.go: Early return in onMessageCreate if bot already reacted (prevents

  duplicate emoji reactions on Discord reconnection).

- bot/bot.go: Add /version slash command with build version injection.

- main.go: Add version variable with ldflags support.

- Makefile: Add dns-fix, test, vet, build-native, pg-*, boot targets.

  Prepend test+vet to deploy pipeline. Add version ldflags to build.

- db/migrations/002_fix_usernames.sql: One-time SQL to backfill old usernames.

- scripts/fix-jail-dns.sh: Script to update jail resolv.conf from 8.8.8.8

  to reachable nameservers (1.1.1.1, 9.9.9.9, 172.16.0.1).

Signed-off-by: Blake Ridgway <blake@blakeridgway.com>

scripts/fix-jail-dns.sh

@@ -0,0 +1,32 @@
+#!/bin/sh
+# Fix DNS for the cyclingbot jail.
+# The jail's resolv.conf currently points to 8.8.8.8 which is unreachable
+# from the 172.16.0.x network. Replace with reachable nameservers.
+#
+# Usage:  sh scripts/fix-jail-dns.sh
+#   or:    ssh root@172.16.0.101 "sh -s" < scripts/fix-jail-dns.sh
+
+JAIL_ROOT="/jails/cyclingbot"
+RESOLV_CONF="${JAIL_ROOT}/etc/resolv.conf"
+
+if [ ! -f "$RESOLV_CONF" ]; then
+    echo "Error: $RESOLV_CONF not found (is the jail running?)"
+    exit 1
+fi
+
+echo "Current contents:"
+cat "$RESOLV_CONF"
+echo ""
+
+cat > "$RESOLV_CONF" << 'EOF'
+nameserver 1.1.1.1
+nameserver 9.9.9.9
+nameserver 172.16.0.1
+search cassville.internal
+EOF
+
+echo "Updated contents:"
+cat "$RESOLV_CONF"
+echo ""
+echo "DNS configuration updated."
+