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/alembic/versions/0002_refresh_token_hash.py

@@ -0,0 +1,23 @@
+"""add refresh_token_hash to sessions
+
+Revision ID: 0002
+Revises: 0001
+Create Date: 2026-04-22
+"""
+from alembic import op
+import sqlalchemy as sa
+
+revision = "0002"
+down_revision = "0001"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column("sessions", sa.Column("refresh_token_hash", sa.Text, nullable=True))
+    op.create_index("ix_sessions_refresh_token_hash", "sessions", ["refresh_token_hash"])
+
+
+def downgrade() -> None:
+    op.drop_index("ix_sessions_refresh_token_hash", table_name="sessions")
+    op.drop_column("sessions", "refresh_token_hash")