v0.18.0

Added

• Optional tags for routines. Routines can now carry a free-form list of
  string labels for grouping and organization. Tags are optional (default empty),
  persisted in the tracked routine.toml, and settable across every surface: REST
  (tags on the create/update bodies), MCP (create_routine/update_routine),
  the CLI (repeatable --tag flag on routines create|replace|update), and the
  web UI (a comma-separated field in the routine form plus a column in the table).
  Blank or whitespace-only tags are rejected with 400 Bad Request. (#502)