refactor(webserver): migrate presentational table/iframe attributes to semantic CSS - #102

…o semantic CSS

Retire the remaining presentational HTML in the default template --
cellspacing=/cellpadding= on every table, width= on td/th (deprecated
since HTML 4.01), width=/height= on table (height was never valid
HTML, it works via quirks mode), and frameborder=/scrolling=/
width="100%" on iframes -- keeping the quirks mode doctype untouched
so the table layout renders exactly as before.

Instead of repeating per-cell utility classes, the recurring page
regions get one semantic class on the container table and structural
child selectors in style.css. All selectors go through the
browser-inserted tbody (table.foo > tbody > tr > td) so nothing leaks
into nested tables, and selector matching is unaffected by quirks
mode:

- table.page: the 3-row skeleton of all 8 main pages (full-size
  table, row alignment, 25px footer cell); the logo / navbar cell
  widths fold into the existing td.logo-cell / td.navbar-cell rules.
- table.navbar-table: the trailing 10px spacers and the 190px
  session-links cell via :nth-last-child, which is robust against
  the leading nav-button cells.
- table.footer-bar: the bottom strip (full width, 40px, centered
  50% cells) and its two iframes (full width, borderless) via a
  descendant selector -- safe, the footer bar nests no tables. The
  log page iframes keep their default border as before.
- table.tab: the 9 rounded-corner frames; the 24px edge cells and
  the tab_top/left/right/bottom backgrounds and white content cell
  are derived from row/cell position. The <caption> is a table
  child, not a tbody child, so it does not disturb row counting.
- table.prefs-pane: the 7 preference panes (350px centered, 22px /
  63px side columns, 25px data rows via tr:not(:first-child) --
  header rows never had the height).
- table.prefs-grid / table.kadnewnode: the two 6px-spacing wrapper
  tables; prefs-grid sets its column width via td:nth-child(2)
  because a rowspan=3 cell makes :last-child ambiguous.

cellspacing/cellpadding zero out globally (table { border-spacing: 0 }
plus padding: 0 on th/td); the three exceptions become spacing1
(login box frame) and pad4 (search form, with a child selector
matching cellpadding's own-cells-only semantics). Genuinely one-off
dimensions (login banner, stats columns, log/stats_tree iframes)
become w*/h* utility classes next to the existing h10..h200 set,
with a `p` suffix for percentages. Pixel sizes on img stay as
attributes -- they are valid, non-presentational HTML. scrolling="no"
(obsolete, no outside-CSS equivalent) is replaced by overflow:hidden
on the body of the two framed documents, footer.php and stats.php.
Also drops the undefined doad-table/kadnewnode dead tokens.

Verified against a running amuleweb: after every intermediate step,
headless-Chromium screenshots of all 9 pages plus the two footer
frames are pixel-identical to the starting point except for dynamic
content (stats graphs, uptime, server user/file counts).