feat: RDP profiles, sessions and viewer

- Protocol::Rdp with RdpConfig (domain, password mode, certificate
  policy, TLS-only fallback, fixed or tab-sized resolution, SOCKS5/HTTP
  proxy, SSH tunnel); migration 008 adds rdp_config and drops the
  protocol CHECK constraint so new protocols no longer need a rebuild.
- Session manager: connect_rdp dials directly, via the shared proxy
  module (proxy password from the secret store) or an SSH tunnel; the
  server certificate goes through the known-hosts check (key type
  rdp-tls); a tab-sized desktop uses the tab's reported pixel size, and
  resizes wait until the server opens Display Control. Rejected NLA
  passwords count as auth failures, so a saved one is asked again.
- The VNC viewer becomes DesktopView for both protocols; a small adapter
  turns its keysyms and pointer masks into RDP scancodes, Unicode keys,
  buttons and wheel events. For RDP, Paste Clipboard types the text.
- Profile editor RDP section, Quick Connect, badges, docs.

Verified against xrdp in the app: logon, desktop, input, and connections
through SOCKS5 and HTTP CONNECT relays. Not verified here: Windows/NLA
servers, the SSH tunnel route, and Display Control resizing (xrdp
0.9.24 never opened the channel).

rust/app/src/app.rs

@@ -259,7 +259,7 @@ impl App {
             (Protocol::Raw, Some(p)) => View::Raw(Box::new(crate::raw_view::RawView::new(&info.id, p))),
             (Protocol::Irc, Some(p)) => View::Irc(Box::new(crate::irc_view::IrcView::new(&info.id, p))),
             (Protocol::Github, Some(p)) => View::Github(Box::new(crate::github_view::GithubView::new(&info.id, &p.display_name))),
-            (Protocol::Vnc, Some(p)) => View::Vnc(Box::new(crate::vnc_view::VncView::new(&info.id, p))),
+            (Protocol::Vnc | Protocol::Rdp, Some(p)) => View::Desktop(Box::new(crate::desktop_view::DesktopView::new(&info.id, p))),
             (_, p) => {
                 let (scroll, size, cursor) = match p {
                     Some(p) => (p.terminal_scrollback, p.terminal_font_size, p.terminal_cursor_style.clone()),
@@ -522,12 +522,12 @@ impl App {
             Event::HostKeyVerify { host, key_type, fingerprint, stored, reply, .. } => {
                 self.prompts.push_back(Prompt::HostKey { host, key_type, fingerprint, stored, reply });
             }
-            Event::VncReady { session } => {
-                if let Some(View::Vnc(v)) = self.s.panes.get_mut(&session).map(|p| &mut p.view) {
+            Event::DesktopReady { session } => {
+                if let Some(View::Desktop(v)) = self.s.panes.get_mut(&session).map(|p| &mut p.view) {
                     v.on_ready();
                 }
             }
-            Event::VncFrame { .. } => {}
+            Event::DesktopFrame { .. } => {}
             Event::VncClipboard { text, .. } => self.remote_clipboard(&text),
         }
     }