feat(web-ui): expose all API preferences, aligned with amuleGUI - #595

Rework the preferences view to cover every category the amuleapi
/preferences endpoint exposes and lay it out like the desktop amuleGUI
PrefsUnifiedDlg.

Structure and layout:
- Tabs follow the desktop page order (General, Connection, Directories,
  Servers, Files, Security, IP2Country, Proxy, Filters, Remote controls,
  Online signature, Advanced); Proxy is its own tab and Kad settings live
  under a Kademlia group in the Servers tab.
- A tab's fields can belong to a different API category (f.cat), so Proxy
  writes into 'connection' and the Kademlia group into 'kademlia'.
- Every field sits in a titled group rendered as a card; cards flow into
  masonry-style columns (up to 3 on wide desktop, 2 on medium, 1 on phones)
  and keep source order, so the phone view is that same sequence.
- One field per row inside a card; the Apply button is centered.

Fields and behaviour:
- New field renderers: select, password (write-only), textarea (shared
  folders), trigger (update_now), plus derived read-only fields (e.g. the
  TCP+3 server-request UDP port, computed client-side, never sent).
- Sub-options are indented and gated by their parent (start-next-file
  children, min free space, ffprobe path, extended UDP / UPnP ports,
  dead-server retries, obfuscation options).
- Capability/parent gating supports several conditions: gatedBy, an inverted
  parent (gatedByNot) and a sibling-equals test (gatedByEq, e.g. the GeoIP
  source select); gated and read-only fields are never sent.
- Passwords are only sent when non-empty; the ms-based reask intervals are
  shown/edited in minutes; udp_disabled is shown as an inverted 'Enable
  Extended UDP port' checkbox.
- Integer fields are clamped to their [min, max] range on Apply (empty or
  out-of-range input snaps to the nearest bound), not just floored at 0.

i18n: all strings under prefs_* in en.json and es.json, kept in sync.
CSS: group cards, masonry columns, sub-option indent, centered actions.