feat: secure notes + password history + custom fields + quick-win bundle

Big feature trio
- Secure notes (kind='login'|'note') reusing the encrypted_password+iv
  pipeline for the body. New sidebar entry, slideover variant (title +
  multiline body), distinct card / table-view rendering, badge in name
  column, copy-content button replacing the password copy on note rows.
- Password history: entries_password_history table keeps up to 20 prior
  ciphertexts per entry. HandleUpdateEntry pushes the pre-update
  encrypted_password into history ONLY when it actually differs from
  the incoming one (JS reuses originalEncrypted bit-for-bit when the
  plaintext is unchanged — avoids spamming history on title/folder edits).
  GET /entries/{id}/history endpoint. Slideover modal lists versions
  with mask/reveal/copy/revert. Master-pw rotation wipes history (old
  ciphertext can't be decrypted with the new key).
- Custom fields: per-entry encrypted JSON array of {label, value,
  is_secret}. Same crypto pipeline as the password. Slideover row UI
  with label/value inputs, secret toggle (eye), copy, delete. Re-
  encryption flows through bulk-import, change-master-password, and
  duplicate.

Quick wins
- Cheatsheet overlay (press '?' or topbar button or Ctrl+K). Lists all
  hotkeys + global / tray / card actions. SVG icons inline so the
  cheatsheet matches the actual app glyphs (no emoji mismatch).
- Open URL button on entry cards: ShellExecute via cmd://app/open-url,
  http(s) only, validates entry.site looks like a real hostname.
- Trash auto-purge: setting "Empty trash after N days" (never/7/30/90).
  DELETE /entries/trash/old?days=N called at every unlock.

Favicon strategy
- Subdomains (chat.deepseek.com, app.X.com…) now try the SLD first
  (deepseek.com.ico) before the full host. DDG often returns a generic
  placeholder for subdomains that passes the byte threshold; the SLD-first
  switch surfaces the real brand icon.
- Cap bumped 64 KB → 256 KB on all three sides (Delphi fetch, server
  endpoint, JS upload). DDG sometimes serves the full-res asset.

UX polish
- Click-outside-slideover: stopPropagation everywhere it bites. Custom
  fields buttons (add / delete / secret toggle / copy / eye) all stop
  the click bubble so the document-level "close on outside click" handler
  doesn't fire when rerender() detaches the target from the DOM.
- Native search-cancel button restyled: cyan accent X via mask-image,
  cursor: pointer, breathing room before the Ctrl+K kbd chip.
- Password history modal: scrollable body, multiline wrapped passwords,
  hover border highlight.
- Cheatsheet panel widened (560 → 720 px) so the descriptions no longer
  ellipsis-clip.
- "+ New" topbar splits into a small dropdown: New login / New note.
- Notes show a "note" badge in table-view name column, italic
  "Encrypted note" placeholder in the username column.

Internals
- duplicateEntry copies kind + custom_fields too (one-line forgotten
  earlier).
- entries_password_history dropped on master-pw rotation — the old
  ciphertexts are unrecoverable with the new key.
- bulk-import re-encryption path includes custom_fields.

CLAUDE.md
- "Entry payload — call sites à toucher ensemble" lists the 6 spots
  to update when adding a new (en)crypted field. Notes the historical
  miss of kind in duplicateEntry and custom_fields in the rotation +
  duplicate.

Repo hygiene
- .gitattributes forces CRLF on Delphi sources (RAD Studio refuses LF).
  text=auto for web frontend / docs, binary for .res / .exe / images.

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

delphi-backend/UMainForm.pas

@@ -16,7 +16,7 @@ interface
 uses
   System.SysUtils, System.Classes, System.UITypes, System.NetEncoding,
   System.StrUtils, System.Generics.Collections,
-  Winapi.Windows,
+  Winapi.Windows, Winapi.ShellAPI,
   FMX.Forms, FMX.Controls, FMX.Controls.Presentation, FMX.StdCtrls,
   FMX.Memo, FMX.Memo.Types, FMX.ScrollBox, FMX.Edit, FMX.Layouts, FMX.Types,
   FMX.Dialogs, FMX.DialogService,
@@ -742,6 +742,22 @@ begin
   else if ACmd = 'app/theme' then
     FBridge.ApplyTitleBarTheme(GetParam('mode') = 'dark')
 
+  // Open the entry's site in the user's default browser. We restrict the
+  // scheme to http(s) so JS can't smuggle a file:// or other handler that
+  // would invoke arbitrary Windows applications.
+  else if ACmd = 'app/open-url' then
+  begin
+    var LUrl := GetParam('url');
+    if (LUrl <> '') and
+       (LUrl.ToLower.StartsWith('http://') or LUrl.ToLower.StartsWith('https://')) then
+    begin
+      ShellExecute(0, 'open', PChar(LUrl), nil, nil, 1);  // SW_SHOWNORMAL = 1
+      LogLine('Opened URL: ' + LUrl);
+    end
+    else
+      LogLine('Refused to open non-http(s) URL: ' + LUrl);
+  end
+
   // ---- Device-bound prefs (DPAPI key/value) ----------------------------
   // Used for prefs that must survive the ephemeral-port reset of the
   // WebView2 localStorage (rememberedUsername, etc.).