feat: statuses and ticket types take any colour from a colour picker

Settings shows a native colour picker (the palette as suggestions)
instead of the list of eleven names. The API takes a palette name, as
before, or any #rrggbb; picking a palette colour still saves its name,
so it keeps its hand-made dark version. A free colour gets one variant
per theme, computed with the `color` library (moved towards white or
black until it contrasts 3:1 with the surface) and applied with
light-dark(): a pale yellow darkens on white, a navy lightens on dark.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/api/schema.gql

@@ -866,6 +866,8 @@ type IssueTypeOption {
 
 input IssueTypeOptionInput {
   archived: Boolean! = false
+
+  """A palette colour (follows the theme) or #rrggbb"""
   color: String!
   icon: String!
   id: String!
@@ -2161,7 +2163,7 @@ type WorkflowStatus {
   archived: Boolean!
   category: StatusCategory!
 
-  """Colour token: slate, violet, green…"""
+  """A palette colour (slate, violet, green…, follows the theme) or #rrggbb"""
   color: String!
 
   """Stable id stored on tickets, e.g. IN_REVIEW"""
@@ -2180,6 +2182,8 @@ type WorkflowStatus {
 input WorkflowStatusInput {
   archived: Boolean! = false
   category: StatusCategory!
+
+  """A palette colour (follows the theme) or #rrggbb"""
   color: String!
   id: String!
   name: String!