feat(studio): rich theme picker (presets + custom colour) + editor 0.11.0

Settings dialog's Theme Plugin section is now a grid of
swatched tiles:

- Built-in (none) — falls back to FaiTheme.light/.dark
- One tile per installed studio.theme.* plugin, each
  showing the plugin's primary/secondary/tertiary as
  live colour dots. Tile loads its preview lazily so a
  dozen installed themes don't block the picker.
- Custom — opens a colour-picker dialog with 12 curated
  Material presets + a hex input + live preview. Selecting
  applies ColorScheme.fromSeed for both brightnesses.

main.dart's _pluginThemes parses a 'custom:#RRGGBB' sigil
in the same notifier slot as plugin capability ids, so the
existing persistence + restoration paths cover the custom
case with no new state.

Bumps editor to 0.11.0 (type-checked port connections +
dynamic card width fix + card-height border allowance) and
Studio to 0.58.0.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

pubspec.lock

@@ -125,10 +125,10 @@ packages:
     description:
       path: "."
       ref: main
-      resolved-ref: "3a6e92fe09ae8f423ab99d990c9459d937810717"
+      resolved-ref: "7b256b5e35204771b8eeca3deb1f4071d86a035b"
       url: "https://git.flemming.ai/fai/studio-flow-editor"
     source: git
-    version: "0.10.2"
+    version: "0.11.0"
   fake_async:
     dependency: transitive
     description: