chainage compute and map view

db/init.sql

@@ -291,6 +291,10 @@ CREATE TABLE IF NOT EXISTS chainage_points (
     created_at TIMESTAMPTZ NOT NULL DEFAULT now()
 );
 CREATE INDEX IF NOT EXISTS idx_chainage_points_project ON chainage_points(project_id);
+-- origin marks generated points ('quick' = the two-point quick assign) so they can
+-- be replaced on the next quick run regardless of the (freely editable) note text.
+ALTER TABLE chainage_points ADD COLUMN IF NOT EXISTS origin TEXT NOT NULL DEFAULT '';
+UPDATE chainage_points SET origin='quick' WHERE origin='' AND note LIKE 'quick:%';
 ALTER TABLE videos ADD COLUMN IF NOT EXISTS chainage_start_m    DOUBLE PRECISION;
 ALTER TABLE videos ADD COLUMN IF NOT EXISTS chainage_end_m      DOUBLE PRECISION;
 ALTER TABLE videos ADD COLUMN IF NOT EXISTS sr_chainage_start_m DOUBLE PRECISION;