refactor(FN-846): rename filename prefixes from kb to fusion

- Switch settings export filename prefix from 'kb' to 'fusion' (e.g. fusion-settings-*.json)
- Switch backup filename prefix from 'kb' to 'fusion' with legacy-safe parsing for existing kb-* backups
- Remove unused ntfy deep-link code and dashboard routing for /project/:id
- Remove dead notifier tests and App test assertions for removed features
- Clean up dashboard command and bin.ts unused variables
- Add changeset for the published package rename

packages/core/src/settings-export.test.ts

@@ -70,7 +70,7 @@ describe("settings-export", () => {
     it("should generate filename with correct format", () => {
       const date = new Date("2026-03-31T12:34:56Z");
       const filename = generateExportFilename(date);
-      expect(filename).toBe("kb-settings-2026-03-31-123456.json");
+      expect(filename).toBe("fusion-settings-2026-03-31-123456.json");
     });
 
     it("should use current date by default", () => {
@@ -78,7 +78,7 @@ describe("settings-export", () => {
       const filename = generateExportFilename();
       const after = new Date();
 
-      expect(filename).toMatch(/^kb-settings-\d{4}-\d{2}-\d{2}-\d{6}\.json$/);
+      expect(filename).toMatch(/^fusion-settings-\d{4}-\d{2}-\d{2}-\d{6}\.json$/);
 
       // Parse the timestamp from filename
       const match = filename.match(/(\d{4})-(\d{2})-(\d{2})-(\d{2})(\d{2})(\d{2})/);