fix(settings): open the docs pages themselves, not their old addresses

The integration runbooks, the Garmin note, the guardian note on a managed
record's connections, the backups admin link and the README's self-hosting
link all pointed at retired docs paths that only resolve through redirects
(or not at all, on a host without them). They now go to the final guide
pages, and the settings tests assert the new addresses.

src/components/settings/integrations/__tests__/fitbit-retirement-notice.test.tsx

@@ -31,7 +31,7 @@ describe("<FitbitRetirementNotice>", () => {
     expect(html).toContain("Google Health reads the same Fitbit and Pixel");
     expect(html).toContain("Everything already imported stays.");
     expect(html).toContain('href="#google-health"');
-    expect(html).toContain("/google-health");
+    expect(html).toContain("/guides/connect-google-health/");
   });
 
   it("says the connection has stopped once the day has come", () => {