feat(dashboard phase1): SSE stream with 15s heartbeat; history paging (50); channel sidebar and nav/footer; OG/Twitter link card endpoint; tail UI rework with infinite scroll and auto-follow pause

internal/store/store.go

@@ -117,6 +117,39 @@ func (s *Store) ListMessagesSince(ctx context.Context, channel string, since tim
 	return out, rows.Err()
 }
 
+// ListMessagesBefore returns up to limit messages for a channel strictly before the given time.
+// Results are returned in ascending chronological order.
+func (s *Store) ListMessagesBefore(ctx context.Context, channel string, before time.Time, limit int) ([]Message, error) {
+    if limit <= 0 {
+        limit = 50
+    }
+    rows, err := s.db.QueryContext(ctx,
+        "SELECT id, channel, author, body, at, msgid FROM messages WHERE lower(channel) = lower(?) AND at < ? ORDER BY at DESC LIMIT ?",
+        channel, before.UTC(), limit,
+    )
+    if err != nil {
+        return nil, err
+    }
+    defer rows.Close()
+    var tmp []Message
+    for rows.Next() {
+        var m Message
+        var at time.Time
+        var msgid sql.NullString
+        if err := rows.Scan(&m.ID, &m.Channel, &m.Author, &m.Body, &at, &msgid); err != nil {
+            return nil, err
+        }
+        m.Time = at
+        if msgid.Valid { m.MsgID = msgid.String }
+        tmp = append(tmp, m)
+    }
+    // Reverse to ascending order
+    for i, j := 0, len(tmp)-1; i < j; i, j = i+1, j-1 {
+        tmp[i], tmp[j] = tmp[j], tmp[i]
+    }
+    return tmp, rows.Err()
+}
+
 // ListRecentMessages returns the most recent N messages for a channel.
 func (s *Store) ListRecentMessages(ctx context.Context, channel string, limit int) ([]Message, error) {
 	if limit <= 0 {