chore(ci): remove Renovate

Dependency updates are handled manually, so the scheduled Renovate job
only cost a daily privileged Docker run on the deploy host. The empty
cache directory it maintained is gone too, and the operations note now
records that updates are manual instead of describing bot behaviour.

docs/operations/cms-error-center.md

@@ -56,9 +56,9 @@ Lenis has been removed; the public site now uses native scrolling. Other used
 runtime libraries remain. Vitest and its coverage provider are upgraded together;
 `clearMocks: false` preserves initialization-time permission contract assertions.
 
-Renovate uses separate development/UI/Vitest groups with manual merge and a
-three-day release age. The existing external Gitea bot configuration is retained.
-Node/pnpm upgrades remain coordinated with Docker and the runner toolchain.
+Dependency updates are manual: Renovate has been removed, so there is no bot
+opening upgrade pull requests. Node/pnpm upgrades remain coordinated with
+Docker and the runner toolchain.
 Obsolete global overrides were removed; a scoped esbuild override remains because
 Drizzle Kit's loader still resolves a vulnerable legacy development-server build.
 The two deprecated esbuild-kit packages remain upstream dependencies of Drizzle