Fix history prepend for multi-parameter plots (e.g. drivable target/value)

[Bilchreis]

Problem

On a drivable module's plot (which shows both value and target series),
shrinking the visible time window and then widening it again only
backfilled history for the value series. target never got its older
data re-prepended.

Root cause

HistoryDB.handle_event("fetch-chart-range", ...) always fetched history
for a single hardcoded parameter — socket.assigns.parameter, which
get_parameter/1 resolves to whichever parameter is literally named
"value". Multi-series plots (e.g. PlotDB.Drivable, whose
param_names/0 returns ["value", "target"]) were never accounted for,
so target's series was silently skipped on every range-based backfill.

Fix

fetch-chart-range now:

• Looks up the plot's full parameter list via PlotDB.param_list/1
  (already used for live-tick updates) instead of the single cached
  parameter assign.
• Resolves each parameter name back to its %Parameter{} struct with a
  new resolve_param/2 helper (handles both bare %Parameter{} and
  %Module{} secop objects).
• Fetches range data and builds trace updates per parameter, then merges
  all seriesUpdates (and any arrayLen) into a single payload via
  merge_trace_updates/1 before pushing one prepend-chart-data-#{id}
  event.

No JS changes needed — the EChartsChart hook already iterates every
entry in seriesUpdates, so it transparently picks up the extra series.