Redesigned frontend: neo-brutalist UI with swipe, keyboard input and animations.

Single-file rewrite of static/index.html preserving the puzzle API contract,
board coordinates and localStorage format. Adds swipe-to-select, keyboard
tracing (type/Backspace/Enter/Esc), juicy tile animations + confetti, and a
light/dark theme toggle.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

zangramru/services/puzzles.py

@@ -239,6 +239,7 @@ class PuzzleGenerator:
             prev = path[0]
             for tile in path[1:]:
                 neigbours[prev].add(tile)
+                neigbours[tile].add(prev)
                 prev = tile
 
         extras = {w: p for w, p in solutions.items() if w not in cover}