FN-5777: remove GitHub star setting and button

Remove the dashboard setting and UI entry points for the GitHub star prompt.

- Remove the Star on GitHub option from settings state types and schema definitions.
- Delete SettingsModal UI, handlers, and styles tied to the star button and related layout.
- Update SettingsModal tests and add a changeset documenting the patch release impact.

Files changed:
 .changeset/FN-5777-removal.md                      |   7 ++
 packages/core/src/settings-schema.ts               |   1 -
 packages/core/src/types.ts                         |   4 -
 .../dashboard/app/components/SettingsModal.css     |  51 +-------
 .../dashboard/app/components/SettingsModal.tsx     | 137 +--------------------
 .../components/__tests__/SettingsModal.test.tsx    |   5 +-
 6 files changed, 13 insertions(+), 192 deletions(-)

Fusion-Task-Id: FN-5777

Fusion-Task-Lineage: 16367ba6-ad22-4ba0-a033-005ccc420c19

packages/core/src/settings-schema.ts

@@ -69,7 +69,6 @@ export const DEFAULT_GLOBAL_SETTINGS = {
   fnBinaryCheckEnabled: true,
   updateCheckFrequency: "daily",
   autoReloadOnVersionChange: true,
-  showGitHubStarButton: true,
   githubTrackingDefaultRepo: undefined,
   modelOnboardingComplete: undefined,
   useClaudeCli: undefined,

packages/core/src/types.ts

@@ -2575,10 +2575,6 @@ export interface GlobalSettings {
    *  useful when the local dev process is the source of truth and shelling
    *  out to an outdated globally-installed binary is unwanted. */
   fnBinaryCheckEnabled?: boolean;
-  /** When false, hides the "Star on GitHub" button in the Settings modal
-   *  header. Defaults to true (visible). The button is also hidden once the
-   *  user has clicked it (tracked client-side in localStorage). */
-  showGitHubStarButton?: boolean;
   /** Global fallback GitHub tracking repo in `owner/repo` format (FN-3868).
    *  Used when a project has no githubTrackingDefaultRepo. */
   githubTrackingDefaultRepo?: string;