feat(upcoming): look up to 30 days ahead, and choose how far

Kommendes liste has always been the next seven days and nothing else. Seven days
is the right walk to take in the morning, and it is still what the view opens on
— but "when does this month get busy" is a different question, and the month grid
answers it with shape rather than in order. So the list now takes a horizon: 7,
14 or 30 days, chosen with a switcher beside the view buttons.

Only the list gets one. A week grid is a week and a month grid is a month; there
is no fortnight for them to show, so the switcher is hidden in those modes.

The choice lives in localStorage next to the mode, under its own key. It is the
same kind of choice as list-or-grid — how you want to look, not a fact about the
work — and it should survive a reload without following you to a phone where
thirty day headings is a very long scroll.

Once the strip is longer than a week the day headings carry the week number.
Thirty days repeat every weekday four times, and "mandag 6. okt" alone does not
say which mandag.

Server side the endpoint already took `?days=` and capped it at 31, so the window
needed nothing — but its row limit was a constant 1000 written for a week. A
month asked for with a week's ceiling would truncate the last days silently, and
a day cut off the end of the answer looks exactly like a day with nothing due, so
the limit now follows the window.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SA1TDmgQZw3AufJqkbwezx

internal/httpapi/tasks_test.go

@@ -285,6 +285,49 @@ func TestTodayAndUpcoming(t *testing.T) {
 	}
 }
 
+// The horizon is the list's, and it is asked for per request: seven days is the
+// default, thirty is what Kommende offers for "when does this month get busy", and
+// anything past the cap is trimmed rather than refused — a client that asks for a
+// year gets a month, not a 400.
+func TestUpcomingHorizon(t *testing.T) {
+	ts := newTestServer(t)
+	ts.bootstrap(t)
+
+	resp, out := ts.do(t, "POST", "/api/v1/tasks", map[string]any{
+		"content":  "om tyve dage",
+		"due_date": userDate(t, 20),
+	})
+	if resp.StatusCode != http.StatusCreated {
+		t.Fatalf("create: %d %v", resp.StatusCode, out)
+	}
+
+	count := func(query string) (int, int) {
+		t.Helper()
+		_, view := ts.do(t, "GET", "/api/v1/upcoming"+query, nil)
+		days, _ := view["days"].([]any)
+		var tasks int
+		for _, d := range days {
+			day, _ := d.(map[string]any)
+			list, _ := day["tasks"].([]any)
+			tasks += len(list)
+		}
+		return len(days), tasks
+	}
+
+	if n, found := count(""); n != 7 || found != 0 {
+		t.Errorf("default horizon returned %d days and %d tasks, want 7 and 0", n, found)
+	}
+	if n, found := count("?days=30"); n != 30 || found != 1 {
+		t.Errorf("days=30 returned %d days and %d tasks, want 30 and 1", n, found)
+	}
+	if n, _ := count("?days=365"); n != 31 {
+		t.Errorf("days=365 returned %d days, want it capped at 31", n)
+	}
+	if n, _ := count("?days=nonsense"); n != 7 {
+		t.Errorf("an unreadable days returned %d days, want the default 7", n)
+	}
+}
+
 func TestSearchFindsAcrossProjects(t *testing.T) {
 	ts := newTestServer(t)
 	ts.bootstrap(t)

internal/httpapi/views_handlers.go

@@ -51,7 +51,8 @@ type upcomingDay struct {
 	Tasks []taskJSON `json:"tasks"`
 }
 
-// handleUpcoming returns the next seven days, one entry per day.
+// handleUpcoming returns the next `days` days, one entry per day, seven by default
+// and at most a month.
 //
 // Empty days are included on purpose: the view is a calendar strip, and a Thursday
 // missing from the response because nothing is due would collapse the layout and
@@ -65,10 +66,14 @@ func (s *Server) handleUpcoming(w http.ResponseWriter, r *http.Request) {
 	from := start.Format("2006-01-02")
 	to := start.AddDate(0, 0, days-1).Format("2006-01-02")
 
+	// The row limit follows the window rather than sitting at a constant, or a
+	// month asked for with the same ceiling as a week would truncate the last days
+	// silently — and a day cut off the end of the answer looks exactly like a day
+	// with nothing due.
 	tasks, err := s.db.ListTasks(r.Context(), user.ID, store.TaskFilter{
 		DueFrom:   from,
 		DueBefore: to,
-		Limit:     1000,
+		Limit:     200 * days,
 	})
 	if err != nil {
 		s.internal(w, r, "upcoming", err)