feat(backup): add MinIO snapshot backups via CLI and scheduler

config/default.yaml

@@ -284,6 +284,24 @@ hooks:
 #     failure_threshold: 2
 #     disk_threshold_mb: 100
 
+# ── Backup ──────────────────────────────────────────────────────────
+# Snapshot sessions.db, vectors.db (optional), and memory/ into a tarball.
+# If MinIO is enabled, upload with `mc` using ephemeral credentials.
+#
+# backup:
+#   enabled: false
+#   interval: "24h"
+#   local_dir: ~/.local/share/flynn/backups
+#   include_vectors: true
+#   minio:
+#     enabled: false
+#     endpoint: localhost:9000
+#     access_key: ${MINIO_ACCESS_KEY}
+#     secret_key: ${MINIO_SECRET_KEY}
+#     bucket: flynn-backups
+#     prefix: flynn
+#     secure: true
+
 # ── Audio ────────────────────────────────────────────────────────────
 # Configure a Whisper-compatible endpoint for audio transcription.
 # Models that support native audio input (Gemini, OpenAI, GitHub) will