Address Gadfly findings on #85

- PublicGardenPage had the same 100vh mobile bug I fixed in the editor — 100dvh
  there too, so the fix is consistent across both full-height pages.
- Cap the toast stack at 4 (drop oldest). Now that error toasts don't auto-
  dismiss, a burst of failures could otherwise grow the stack unbounded and push
  the newest — the one that just happened — off-screen.
- Hoist the From/To date-input styling to a shared dateInputClass const so the
  two don't drift.

Not taken: reusing safeRedirectPath for the 401 redirect (it validates an
incoming redirect param, it doesn't build the outgoing one — the two uses don't
overlap), and refactoring the three-branch filter spread (it's clear at three
fields; a helper earns its keep when there are more).

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01H3zbym8Doka2d7D48maSgZ

web/src/pages/PublicGardenPage.tsx

@@ -53,7 +53,7 @@ export function PublicGardenPage() {
   }
 
   return (
-    <div className="flex h-[calc(100vh-8rem)] flex-col gap-3">
+    <div className="flex h-[calc(100dvh-8rem)] flex-col gap-3">
       <div className="flex flex-wrap items-center gap-2">
         <h1 className="truncate text-lg font-semibold tracking-tight" title={garden.name}>
           {garden.name}