Stage 7 polish (round 2): layout/zoom/tab-bar/hint/check fixes

- nav bar grows ONLY in game (other screens: minimal nav, content fills); tab bar always bottom
- tab bar: tighter icon/label spacing, bigger icons, hint badge on the icon corner
- board zoom reworked to width-based (real native scroll, fixes Safari/Chrome) + constant cqw labels; pinch & swipe-to-history dropped (conflict), double-tap kept, history via menu
- beginner bonus labels shrunk to fit cells
- Draw opens exchange directly (no confirm); confirm popovers restyled like the hamburger dropdown (vertical); removed the floating direction toggle
- pending tiles darker bg (no outline); last-word dark-tile highlight (static / 1s flash)
- check button disabled for <2/>15 chars, already-checked, or 5s cooldown
- global user-select:none (inputs exempt); docs updated; TODO-4 alphabet-on-wire

ui/src/app.css

@@ -27,8 +27,8 @@
   --tile-bg: #f4e2b8;
   --tile-edge: #d8c190;
   --tile-text: #2a2113;
-  --tile-pending: #ffe7a3;
-  --tile-recent: #fff6d8;
+  --tile-pending: #f2cf73;
+  --tile-recent: #c8a85c;
   --prem-tw: #e06a5b; /* triple word */
   --prem-dw: #efa6a0; /* double word + centre */
   --prem-tl: #4f8fd6; /* triple letter */
@@ -66,8 +66,8 @@
     --tile-bg: #d9c79a;
     --tile-edge: #b6a473;
     --tile-text: #20190d;
-    --tile-pending: #f0d98f;
-    --tile-recent: #4a4636;
+    --tile-pending: #d8b75e;
+    --tile-recent: #7a6638;
     --prem-tw: #b1493d;
     --prem-dw: #8c5450;
     --prem-tl: #34608f;
@@ -130,6 +130,15 @@ body {
 
 #app {
   height: 100%;
+  /* No text selection anywhere by default; inputs opt back in below. */
+  user-select: none;
+  -webkit-user-select: none;
+}
+
+input,
+textarea {
+  user-select: text;
+  -webkit-user-select: text;
 }
 
 button {