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>

main.go

@@ -13,6 +13,9 @@ import (
 	"cycling-discord-bot/db"
 )
 
+// Build version, set via ldflags at build time (see Makefile)
+var version = "dev"
+
 func main() {
 	_ = godotenv.Load()
 
@@ -26,7 +29,7 @@ func main() {
 	}
 	defer database.Close()
 
-	b, err := bot.New(token, database, guildID)
+	b, err := bot.New(token, database, guildID, version)
 	if err != nil {
 		log.Fatalf("create bot: %v", err)
 	}
@@ -39,6 +42,8 @@ func main() {
 	// Give the session a moment to identify before registering commands
 	time.Sleep(500 * time.Millisecond)
 
+	log.Printf("starting cycling-discord-bot version %s", version)
+
 	if err := b.RegisterCommands(); err != nil {
 		log.Fatalf("register commands: %v", err)
 	}