Add vision-LLM import pipeline for hex terrain classification

Adds a 3-phase pipeline to populate a HexMap from a source image using
Claude's vision capabilities instead of naive pixel-color matching:

Phase 1 (extract-submaps): crops annotated submap PNGs per hex,
  including center + 6 neighbours with SVG overlay.
Phase 2: Claude classifies submaps in a Code session, writing
  classifications.json — resumable across sessions.
Phase 3 (import-from-json): reads classifications.json into the DB.

Also adds assemble-map.ts to reconstruct a full image from a Leaflet
tile pyramid (used to recover the Aventurien source map from kiepenkerl).

Adds CLAUDE.md documenting the approach, scale constants
(PIXELS_PER_MEILE=8, hexSize=40 = 10 Meilen/Hex), and the
Nord/Mitte/Süd region split for the Aventurien map.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -4,3 +4,7 @@ dist-server/
 *.log
 tiles/
 data/*.db
+
+# Pipeline artefakte — lokal erzeugte Karten, Tiles, Submaps
+pipeline/source/
+pipeline/submaps/