Show a colour-coded team picker instead of cycling with T

T used to silently cycle Model.activeTeamID through the caller's teams with
no visible list of choices. It now opens a full picker (modelled on the
existing user picker) listing every team plus "All teams", each with a
stable identity colour from a new six-colour theme palette. The same colour
now also shows as a bullet next to "team: <name>" in the header, so the
active team stays visible without opening the picker.

Adds an Identity palette to the theme package (six hues, skipping the ones
that already mean firing/critical), Styles.TeamColor to pick one by team id,
and identity_1..6 as theme-file tokens alongside the existing twelve so a
fully custom theme can still set every token.

internal/tui/styles.go

@@ -125,6 +125,17 @@ func (s Styles) IncidentStatus(status string) lipgloss.Style {
 	}
 }
 
+// TeamColor picks a stable identity colour for a team id, so the same team
+// always reads the same colour without the server needing to store one.
+func (s Styles) TeamColor(teamID int64) lipgloss.Style {
+	n := int64(len(s.theme.Identity))
+	i := teamID % n
+	if i < 0 { // ids are never negative in practice, but % can still return one
+		i += n
+	}
+	return lipgloss.NewStyle().Foreground(s.theme.Identity[i])
+}
+
 // ── Embedded bubbles components ────────────────────────────────────────────
 //
 // Each ships its own hardcoded palette, so a theme that stopped at this