refactor: 30-day defaults for all expiry settings

- QUEUE_MAX_AGE: 48h -> 30 days (per-client queue entry expiry)
- MESSAGE_MAX_AGE: replaces count-based MAX_HISTORY with time-based
  30-day message expiry
- SESSION_IDLE_TIMEOUT: 24h -> 30 days

All expiry is now time-based (30 days) as requested.

Closes #40

internal/handlers/handlers.go

@@ -31,7 +31,7 @@ type Params struct {
 	Healthcheck *healthcheck.Healthcheck
 }
 
-const defaultIdleTimeout = 24 * time.Hour
+const defaultIdleTimeout = 30 * 24 * time.Hour
 
 // Handlers manages HTTP request handling.
 type Handlers struct {
@@ -205,8 +205,7 @@ func (hdlr *Handlers) runCleanup(
 }
 
 // pruneQueuesAndMessages removes old client_queues entries
-// per QUEUE_MAX_AGE, rotates messages per MAX_HISTORY, and
-// cleans up orphaned messages.
+// per QUEUE_MAX_AGE and prunes messages per MESSAGE_MAX_AGE.
 func (hdlr *Handlers) pruneQueuesAndMessages(
 	ctx context.Context,
 ) {
@@ -230,18 +229,22 @@ func (hdlr *Handlers) pruneQueuesAndMessages(
 		}
 	}
 
-	maxHistory := hdlr.params.Config.MaxHistory
-	if maxHistory > 0 {
-		rotated, err := hdlr.params.Database.
-			RotateChannelMessages(ctx, maxHistory)
+	messageMaxAge := hdlr.params.Config.MessageMaxAge
+	if messageMaxAge > 0 {
+		msgCutoff := time.Now().Add(
+			-time.Duration(messageMaxAge) * time.Second,
+		)
+
+		pruned, err := hdlr.params.Database.
+			PruneOldMessages(ctx, msgCutoff)
 		if err != nil {
 			hdlr.log.Error(
-				"message rotation failed", "error", err,
+				"message pruning failed", "error", err,
 			)
-		} else if rotated > 0 {
+		} else if pruned > 0 {
 			hdlr.log.Info(
-				"rotated old messages",
-				"deleted", rotated,
+				"pruned old messages",
+				"deleted", pruned,
 			)
 		}
 	}