v4.2.0

• Added optional per-metering-point current month consumption and cost sensors, controlled by a dedicated integration option.
• Added a Norway-only Norgespris consumption limit sensor when the source value is available from Fortum metering-point data.
• Refactored coordinator/session runtime ownership by introducing SessionManager and splitting coordinators into dedicated modules, improving setup/runtime consistency.
• Refined authentication and coordinator logging to reduce debug noise while preserving useful diagnostics context.
• Expanded contributor and API reference documentation with architecture notes and sanitized Fortum API examples.