v0.4.0 — Docker release images, cursor pagination, temporal memory views

• Docker image for bind-mounted operation: all state (config file, database directory) lives as operator-owned files on the host, nothing in the image; setup guide in docs/DOCKER.md.
• Multi-arch release images (linux/amd64 and linux/arm64) published to GHCR automatically when a GitHub release is published.
• The CLI now exits with a single clear line instead of a traceback when the config file is missing or the database directory is missing or not writable.
• GET /memory, GET /events, and GET /topics now paginate by cursor via the opaque X-Next-Cursor response header; offset now returns HTTP 400 instead of being silently ignored, and listing order is total (updated_at DESC plus an id/topic tiebreaker) so pages stay stable and disjoint.
• The current temporal search view now demotes naturally-expired facts (score x0.70, applied after the relevance gates) rather than hiding them, and the injected-context retrieval path compiles with the current view while drill-down memory tools and the learner still search with all.
• Graceful shutdown now cancels a wedged background learning job after a 5-second grace, bounding Ctrl-C latency independently of learning.timeout_seconds.