Scroll speeds below 1 dot per second

scroll_speed is now a float (0.05-30 dots per second, e.g. 0.25 = one dot
every 4 s). Page format 5; version 4 pages are converted, version 3 goes
through version 4.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/esp32/web/web_page.h

@@ -378,7 +378,7 @@ function peElems(){const d=$('pe_elems');d.innerHTML='';d.append(mk('datalist',{
   if(TEXTTYPES.includes(e.type)){
    row(...pos,field('Align',sel(e,'align',[['left','left'],['center','center'],['right','right']])),field('Font',sel(e,'font',fonts)),ovl);
    row(field('Scroll in a window of',inp(e,'scroll_width','number',{style:'width:5em',min:0,max:168})),'dots (0: off), at',
-    inp(e,'scroll_speed','number',{style:'width:4em',min:1,max:30}),'dots per second')}
+    inpf(e,'scroll_speed',{style:'width:5em',min:0.05,max:30}),'dots per second (0.25: one every 4 s)')}
   else if(e.type=='bar')row(...pos,field('Align',sel(e,'align',[['left','left'],['center','center'],['right','right']])),ovl);
   else row(...pos,ovl);
   box.append(...rows);d.append(box)})}