* Replace OpenLayers.Control.Snapping with the OL10 Snap interaction.
* Render snap features as a solid orange overlay while snapping is active.
* Drop the manual refresh button: getSnappingData() now runs automatically
  on moveend and on layer-tree visibility changes (the
  snapLayersRefreshable state and snapping.refreshable event are gone,
  no consumers remained).
* OL10 Snap exposes a single vertex flag and a single pixelTolerance, so
  snap_vertices is OR-ed with snap_intersections and pixelTolerance is
  max(snap_vertices_tolerance, snap_segments_tolerance). Worth flagging
  for projects that configure vertex vs intersection independently.
* Public reorderSnapInteraction() lets future callers re-add the Snap
  interaction so OL processes it before any recently-added Draw / Modify
  / Translate. No-op when snap is inactive.

Tests:
* snap.spec.js: remove three WFS 1.1.0 / SRSNAME / datum-shift tests that
  exercised the OL2 snap WFS path (replaced by OL10 GeoJSON parsing).
  Strip refresh-button click / disabled-state assertions from the snap
  panel test now that refresh is automatic.

This PR ships the snap infrastructure but does not visibly engage with
the OL2 edition Draw / Modify yet. Snapping starts to actually snap once
the follow-up OL10 edition migration lands.

* Replace OpenLayers.Control.DrawFeature / ModifyFeature / SelectFeature
  with OL10 Draw, Modify and Select interactions. The OL2 vector edit
  layer becomes an OL10 VectorLayer / VectorSource on mainLizmap.map.
* Auto-activate Modify after a feature is drawn, including for point
  layers. Feature highlights use the OL10 draw layer.
* Route WMS extent / size queries through the OL10 view. Required
  because the OL10 map is now the source of truth for the visible
  viewport during edition.
* New modules/Edition.js owns the WKT bridge between the digitizing
  module and the hidden geometry form field, and emits user-facing
  toasts via #lizmap-editing-message (the legacy #lizmap-edition-message
  is still used for save-success / error toasts).
* Duplicate toast dispatches removed from legacy/edition.js so the
  "Edit vertices" / "Draw on the map" toast no longer appears twice.
* For point edition the digitizing toolbar is hidden; drawing begins
  automatically on click.
* New baseline locale keys: edition.toolbar.redraw plus four
  digitizing.toolbar.<tool>.help keys (edit / split / rotate / scaling).
* Remove ~120 lines of dead OL2 split helpers from legacy/edition.js
  (afterReshapeSpliting, beforeFeatureSpliting, afterFeatureSpliting and
  their editCtrls.reshape / editCtrls.featsplit entries).

Builds on the snapping migration. The new digitizing module calls
mainLizmap.snapping.reorderSnapInteraction() after adding interactions,
so the OL10 Snap follows each new Draw / Modify / Translate.

Tests:
* 9 spec files updated for OL10 map / interactions (clickOnMapLegacy
  → clickOnMap, mapOl2 → map, #map → #newOlMap, waitForFunction guards
  for Select/Modify).
* edition-form.spec.js: "must allow modification without creation"
  now expects #lizmap-editing-message (the new id) for the on-form
  edit-vertices toast.
* editing-copy-paste-geometry.spec.js: mark the 11 interaction tests
  test.fixme(). They cover behaviour that needs the OL10 GeometryCopy
  port (lands in the follow-up Copy/Paste PR).
* draw.spec.js: mark "Length and angle constraints" test.fixme() —
  the distance/angle constraint feature is deferred to a follow-up PR.

Deferred to follow-up PRs: reshape, parallel offset, move (in edition),
distance/angle drawing constraints, split-with-server-save (the
digitizing-split button is therefore hidden in edition context for now,
remains available in draw context), ReverseGeom port, draw.spec.js
new-tool tests and pages/drawpage.js new-tool locators.