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>

backend/app/workers/backup.py

@@ -0,0 +1,25 @@
+"""
+Daily encrypted backup job — runs the backup.sh script inside the container.
+The script does: pg_dump | gzip | gpg symmetric AES-256 → /app/backups/
+"""
+import asyncio
+import structlog
+
+logger = structlog.get_logger()
+
+
+async def backup_job() -> None:
+    try:
+        proc = await asyncio.create_subprocess_exec(
+            "bash", "/app/scripts/backup.sh",
+            stdout=asyncio.subprocess.PIPE,
+            stderr=asyncio.subprocess.STDOUT,
+        )
+        stdout, _ = await proc.communicate()
+        output = stdout.decode().strip() if stdout else ""
+        if proc.returncode == 0:
+            logger.info("backup_complete", output=output)
+        else:
+            logger.error("backup_failed", returncode=proc.returncode, output=output)
+    except Exception as exc:
+        logger.error("backup_error", error=str(exc))