Add pension PDF upload, parsing, and fund summary API

Backend: parse BAC pension statement PDFs (VOL, ROP, FCL) via
pdftotext, store snapshots with duplicate detection, reject
credit card statements. Endpoints: POST /upload, GET /snapshots,
GET /fund-summary.

Frontend: wire up drag-and-drop upload, load real balances and
rendimientos from API, show upload results with error/duplicate
feedback.

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

backend/app/api/v1/router.py

@@ -9,6 +9,7 @@ from app.api.v1.endpoints import (
     exchange_rate,
     import_transactions,
     notifications,
+    pensions,
     salarios,
     settings,
     tokens,
@@ -28,3 +29,4 @@ api_router.include_router(settings.router)
 api_router.include_router(budget.router)
 api_router.include_router(notifications.router)
 api_router.include_router(salarios.router)
+api_router.include_router(pensions.router)