Override partial of ADR 0011: Tiingo Power pre-designation is invalidated
by 2026 pricing reality (~30 USD/mo, not 10) AND by ToS (Power tier is
internal-use only; multi-tenant proxy requires Commercial 500+/mo plus a
redistribution license).
Alpha Vantage Premium 49.99 USD/mo retained as direct Yahoo replacement,
under suspensive condition of written ToS authorization for commercial
multi-tenant proxy use.
Phase 2 smoke test surfaced a key finding: Alpha Vantage silently accepts
Yahoo-style .TO ticker suffix as alias of .TRT, removing the need for any
mapping table. Drop-in compatible with existing Yahoo provider code.
Refs maximus-api#41
