Add Solarbank 3 E2700 Pro support

[MrChurch]

Summary

Add direct BLE support for the Solarbank 3 E2700 Pro (A17C5), tested with firmware 1.0.7.1.

This PR intentionally covers the device library only. It does not add Home Assistant entities, system-level Solarbank aggregation, cloud metadata handling, or other integration-specific behavior.

What changed

• Add the Solarbank 3 secure-conference protocol helpers:
  • dynamic secp256r1 ECDH per connection
  • session AES-GCM authentication with the captured AAD
  • authenticated 4022 account authentication
  • authenticated 4027 client-security authentication
  • encrypted 4040 telemetry request
• Add Solarbank 3 telemetry decoding for the observed A17C5 fields, including typed float values.
• Add device-level controls:
  • set_schedule(power_w): seven-day 405e schedule, 0-1200 W in 50 W steps
  • set_max_load(max_load_w): 4080 values 350, 600, 800 and 1200 W
• Accept the 03000f encrypted session packet pattern used by the Solarbank 3.
• Document the required explicit Anker account ID constructor argument.
• Add protocol, telemetry mapping and mock end-to-end authentication tests.

Validation

• 10 targeted tests pass (tests/test_solarbank3.py and tests/test_prime.py).
• Targeted Ruff F/E checks pass for all changed Python files.
• Python bytecode compilation passes for SolixBLE and tests.
• The device-level protocol was verified against an A17C5 running firmware 1.0.7.1.

The full existing test suite still has two timing-sensitive automatic reconnect failures in the pre-existing C300/Prime tests; they reproduce independently of the Solarbank 3 tests and are unrelated to this change.