fix(go): align adults cell class names with Python; un-underline Pay buttons

- Map unpaid|partial → cell-unpaid (or cell-unpaid-current for current
  month) and surplus → cell-overridden, matching Python's Jinja logic;
  avoids emitting non-existent cell-partial/cell-surplus classes that
  caused Pay buttons to escape the table.
- Add text-decoration: none to .pay-btn so anchor-based Pay links don't
  show the default underline.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

go/internal/web/static/css/app.css

@@ -177,6 +177,7 @@ tr:hover {
     transform: translateY(-50%);
     background: #ff3333;
     color: white;
+    text-decoration: none;
     border: none;
     border-radius: 3px;
     padding: 2px 6px;

go/internal/web/templates/adults.tmpl

@@ -59,7 +59,7 @@
       <td class="member-name">{{$row.Name}}</td>
       {{range $i, $cell := $row.Months}}
       <td data-month-idx="{{$i}}" title="{{$cell.Tooltip}}"
-          class="cell-{{$cell.Status}}{{if and (or (eq $cell.Status "unpaid") (eq $cell.Status "partial")) (ge $cell.RawMonth $.Data.CurrentMonth)}} cell-unpaid-current{{end}}{{if $cell.Overridden}} cell-overridden{{end}}">
+          class="{{if eq $cell.Status "empty"}}cell-empty{{else if and (or (eq $cell.Status "unpaid") (eq $cell.Status "partial")) (ge $cell.RawMonth $.Data.CurrentMonth)}}cell-unpaid-current{{else if or (eq $cell.Status "unpaid") (eq $cell.Status "partial")}}cell-unpaid{{else if eq $cell.Status "ok"}}cell-ok{{end}}{{if $cell.Overridden}} cell-overridden{{end}}">
         {{$cell.Text}}
         {{if and (or (eq $cell.Status "unpaid") (eq $cell.Status "partial")) (lt $cell.RawMonth $.Data.CurrentMonth)}}
         <a class="pay-btn" href="{{qrHref $.Data.BankAccount $cell.Amount $row.Name $cell.RawMonth}}">Pay</a>
@@ -77,7 +77,7 @@
     <tr class="totals-row" style="font-weight: bold; background-color: #111; border-top: 2px solid #333;">
       <td style="text-align: left; padding: 6px 8px;">TOTAL</td>
       {{range $i, $t := .Data.Totals}}
-      <td data-month-idx="{{$i}}" data-raw-month="{{index $.Data.RawMonths $i}}" class="cell-{{$t.Status}}" style="padding-top: 4px; padding-bottom: 4px;">
+      <td data-month-idx="{{$i}}" data-raw-month="{{index $.Data.RawMonths $i}}" class="{{if eq $t.Status "ok"}}cell-ok{{else if eq $t.Status "unpaid"}}cell-unpaid{{else if eq $t.Status "surplus"}}cell-overridden{{end}}" style="padding-top: 4px; padding-bottom: 4px;">
         <span style="font-size: 0.6em; font-weight: normal; color: #666; text-transform: lowercase; display: block; margin-bottom: 2px;">received / expected</span>
         {{$t.Text}}
       </td>