Complete Phase 3, Phase 5 polish and hardening

Phase 3 — Investments:
- Multi-currency support: holdings track purchase currency, FX rates convert to base for totals
- Capital gains report using UK Section 104 pool method, grouped by tax year
- Capital Gains tab added to Reports page

Phase 5 — Polish & Hardening:
- Mobile-responsive layout: bottom nav, sidebar hidden on mobile, logo in TopBar, compact header buttons, hover-only actions now always visible on touch
- Backup system: encrypted GPG backups via backup.sh, nightly scheduler job, admin API (list/trigger/download/restore), Settings UI with drag-to-restore confirmation
- Docker entrypoint with gosu privilege drop to fix bind-mount ownership on fresh deployments
- OWASP fixes: refresh token now bound to its session (new refresh_token_hash column + migration), CSRF secure flag tied to environment, IP-level rate limiting on login, TOTPEnableRequest Pydantic schema replaces raw dict
- AES-256-GCM key rotation script (rotate_keys.py) with dry-run mode and atomic DB transaction
- CLAUDE.md added for AI-assisted development context
- README updated: correct reverse proxy port, accurate backup/restore commands, key rotation instructions

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/pages/accounts/AccountList.tsx

@@ -99,7 +99,7 @@ export default function AccountList() {
       </div>
 
       {nw && (
-        <div className="grid grid-cols-3 gap-4">
+        <div className="grid grid-cols-1 sm:grid-cols-3 gap-4">
           {[
             { label: "Total Assets", value: nw.total_assets, positive: true },
             { label: "Total Liabilities", value: nw.total_liabilities, positive: nw.total_liabilities === 0 },
@@ -253,7 +253,7 @@ function AccountGroup({
                   )}
                 </div>
 
-                <div className="flex items-center gap-1 opacity-0 group-hover:opacity-100 transition-opacity shrink-0">
+                <div className="flex items-center gap-1 opacity-100 sm:opacity-0 sm:group-hover:opacity-100 transition-opacity shrink-0">
                   <button
                     onClick={() => onEdit(account)}
                     className="p-1.5 rounded text-muted-foreground hover:text-foreground hover:bg-secondary"