WSA Implementation

[mudhoney]

Adds WSA as an event source and migrates all events-state handling from the legacy eventsState tree to the new
event_selections + event_visibility_selections shape, end to end.

WSA source

• Enable the WSA source with the Magnetic Connectivity event type, its 2-letter pin, and colors.
• Add the MC marker pin so WSA events stop falling back to UNK.png.
• Support multi-ring event footprints (array of rings) throughout.

New events payload shape

• Adopt event_selections + event_visibility_selections as the request shape for postScreenshot/postMovie.
• takeScreenshot gains an optional semicolon-separated event_selections= GET var, preferred over legacy events=.
• Both screenshot and movie endpoints persist the new-shape blob so rows rehydrate identically.
• Raise the max-selections validation limit.

EventContext

• Rewrite EventContext to read events lazily per frame (memory-bounded) instead of all at once.
• Consume the events API's {dx,dy} rotation deltas directly and apply them per frame.
• Request frames_with_selections?withDelta so the upstream returns those deltas.
• Drop selections for any source whose marker_visibility is false.

Retire the legacy path

• Extract EventTypeCatalogue and LegacyEventsStringParser from the old classes.
• Delete EventSelections; Timeline now takes canonical paths via an array constructor.
• Remove the obsolete getEventsBatch conversion path.

New endpoint + stats

• Add eventsDataCoverage (POST) as a simpler event-timeline coverage endpoint.
• Register eventsDataCoverage in usage statistics.

Data migration

• Add dry-run-by-default migration scripts for screenshots, movies, and client_states.
• Update client_state.schema.json to require the new fields and drop eventLayers.

Config / tooling / docs

• Raise the events API timeout and chunk size so large movies don't time out.
• Add a Makefile with dev/test, migration, and requeue-movie shortcuts.
• Update the OpenAPI docs and client_state test fixtures to the new shape.

⚠️ Before merge

• Revert 539ba45 — it points Config.Example.ini at events.necdet.helioviewer.org for stack testing and must not ship (the
  default should stay events.helioviewer.org).

Follow-ups (not in this PR)

• Run the migrations in a maintenance window, then delete EventsStateManager (kept only as the migration adapter).