Code review cleanup: cache placement/adjacency, drop dead code

- Cache choosePlacement and adjacentTile results per (id,dir); invalidate
  on addTile. Avoids O(n^3) placement scoring on every pointermove.
- setCurrent now re-renders only affected navs (prev + new) instead of
  refreshAllNav; remove refreshAllNav entirely.
- Add pointercancel handler so interrupted touch/trackpad gestures don't
  leave a stuck drag.
- Remove dead code: placeRect, photoConnections + /api/photo route and
  THUMBS const on server, dangling info var in pointerup.
- Trim .gitignore, remove .DS_Store, bump cache-bust to ?v=20.

1 files changed, 3 insertions, 35 deletions

diff --git a/.gitignore b/.gitignore
index fd3dbb5..6659201 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,36 +1,4 @@
-# See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
-
-# dependencies
-/node_modules
-/.pnp
-.pnp.js
-.yarn/install-state.gz
-
-# testing
-/coverage
-
-# next.js
-/.next/
-/out/
-
-# production
-/build
-
-# misc
+node_modules/
 .DS_Store
-*.pem
-
-# debug
-npm-debug.log*
-yarn-debug.log*
-yarn-error.log*
-
-# local env files
-.env*.local
-
-# vercel
-.vercel
-
-# typescript
-*.tsbuildinfo
-next-env.d.ts
+*.log
+.env*