Feature: Add interactive filters in generated HTML (species / condition / height)

[aplgr]

Goal

Add user-facing filters to the generated offline HTML so users can focus on subsets, e.g.:

• species (Art) filter
• condition (Zustand) filter (range + quick toggles like “dead only” / “hide dead”)
• height/size filter (range)

Why

In larger groves, it’s hard to spot patterns. Filters make the visualization much more useful without changing the underlying CSV format.

Scope (MVP)

• Add a small “Filters” panel (collapsible) in the HTML UI.
• Species: multi-select (derived from the dataset).
• Condition: range slider + toggle for including/excluding 0 (dead) and “no data”.
• Height: range slider.
• Filters apply immediately (no reload) and work across timeline slices.
• Persist filter settings in localStorage.

Acceptance criteria

• Filters update the chart instantly (no page reload)
• Timeline/slider still works with filters enabled
• Tooltips and legends remain consistent
• Default view (no filters) is unchanged
• Settings persist across reload

Notes / hints

Implementation can be “hide points/cells” rather than re-computing the full dataset:

• For scatter points: filter out entries before feeding ECharts or set them to hidden.
• For heatmap cells: treat filtered-out cells as “no data” so the grid stays stable.
  Keep the UI calm/minimal (fits the existing aesthetic).