Bump version to 1.7.6

[Bre77]

Intent

• Bump version/__version__ from 1.7.5 to 1.7.6 to release the three unreleased commits on main
• No behavior changes in this PR itself; pushing the v1.7.6 tag afterward is what publishes to PyPI (.github/workflows/python-publish.yml fires on tag push, not on merge)

Changes going into 1.7.6

• fix(vehicle): align navigation_gps_request order default across transports (fix(vehicle): align navigation_gps_request order default across transports #83)
• fix(energy): raise SignedCommandRequired from cloud-only island mode commands (fix(energy): raise SignedCommandRequired from cloud-only island mode commands #84)
• docs(teslemetry): correct find_authorized_clients reliability claim (docs(teslemetry): correct find_authorized_clients reliability claim #82)

Semver note for review

• fix(energy): raise SignedCommandRequired from cloud-only island mode commands #84 changes set_island_mode/go_off_grid/reconnect_grid from a silent unsigned no-op to unconditionally raising SignedCommandRequired - a behavior change for any caller not on the signed local path. Treated as patch here since the prior no-op never actually actuated the contactor, but flagging in case a minor (1.8.0) is preferred instead.