Add accounts expansion, analytics, exchange rates, API tokens, PWA support, and UI overhaul

- Expand Account model with account_type (pension, savings, liability, crypto), new banks/currencies (BTC, XMR, FCL, ROP, VOL, MEMP, MPAT, MORTGAGE), and next_payment field
- Add exchange rate endpoint (BCCR integration), analytics endpoint, paste-import for transactions, and API token management
- Add PWA manifest, service worker, and app icons
- Redesign dashboard, transactions, transfers, and login pages with theme support
- Add billing cycle selector, confirm dialog, and paste import modal components
- One-time DB reset in deploy workflow for schema migration

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/api/v1/endpoints/exchange_rate.py

@@ -0,0 +1,29 @@
+from fastapi import APIRouter, Depends, HTTPException
+from sqlmodel import Session
+
+from app.auth import get_current_user
+from app.db import get_session
+from app.models.models import ExchangeRateRead
+from app.services.exchange_rate import get_current_rate, get_rate_history
+
+router = APIRouter(prefix="/exchange-rate", tags=["exchange-rate"])
+
+
+@router.get("/", response_model=ExchangeRateRead)
+def current_rate(
+    session: Session = Depends(get_session),
+    _user: str = Depends(get_current_user),
+):
+    rate = get_current_rate(session)
+    if not rate:
+        raise HTTPException(status_code=503, detail="Exchange rate unavailable")
+    return rate
+
+
+@router.get("/history", response_model=list[ExchangeRateRead])
+def rate_history(
+    days: int = 30,
+    session: Session = Depends(get_session),
+    _user: str = Depends(get_current_user),
+):
+    return get_rate_history(session, days)