Split calculator into tabs and use dynamic spread

Reorganize the single-scroll page into three purpose tabs (Rekenmodel,
Live dag-strategie, Historie) with the Parameters panel as a persistent
sidebar. Tab state is persisted in localStorage and charts are resized on
activation to avoid 0px canvases in hidden panels; print CSS keeps the full
report.

Also replace the legacy fixed EUR 0,15 spread in the scenario comparator and
payback chart with the dynamic market spread (peakPrice - refPrice), matching
the rest of the tool, and make the related labels reflect it live.

Add .claude/launch.json for local static-preview.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.claude/launch.json

@@ -0,0 +1,11 @@
+{
+  "version": "0.0.1",
+  "configurations": [
+    {
+      "name": "static",
+      "runtimeExecutable": "python3",
+      "runtimeArgs": ["-m", "http.server", "4567"],
+      "port": 4567
+    }
+  ]
+}