feat(reader): relocate back-to-location, add recenter control, wrap bottom bar on small windows

- Back-to-location moves from the topbar (where it sat between Back
  and the title, too subtle and disconnected from navigation) into
  both bottom-bar rows, beside the page-back arrow — the natural
  'go back' cluster. New icon: a location pin, clearly distinct from
  the back arrow and page controls. Appears only when the stack has
  a return target; Alt+← unchanged.
- New recenter button in the fixed-layout row (crosshair icon, next
  to zoom): resets pan offsets while keeping the current zoom —
  backed by foliate's new recenter() (1c812e8), which zeroes the
  wrapper translate and re-syncs the spread side.
- Both bottom-bar rows wrap gracefully on narrow windows instead of
  overflowing/h-scrolling: controls are grouped (paging+back | slider |
  fit+zoom+magnifier+recenter | pointer mode | spread | progress+TOC)
  so groups flow to a second line at small widths; the slider shrinks
  first (grow + min-width), everything else stays whole. Fixed-layout
  row drops its overflow-x-auto.

package.json

@@ -12,7 +12,7 @@
     "dev": "npm run build:ts:dev && npm run build:css"
   },
   "dependencies": {
-    "@bookhoard/foliate-js": "git+https://github.com/john-okeefe/foliate-js.git#86e234d",
+    "@bookhoard/foliate-js": "git+https://github.com/john-okeefe/foliate-js.git#1c812e8",
     "alpinejs": "^3.15.8",
     "chart.js": "^4.5.1",
     "highlight.js": "^11.11.1",