fix: clarify backend setup names

[subzeroid]

Summary

• Rename the public setup/config backend label from hiker to hikerapi while keeping legacy hiker configs and flags compatible.
• Add the HikerAPI token URL directly to the setup prompt.
• Surface a clear aiograpi optional-dependency install hint, including pipx inject insto aiograpi for existing installs.
• Allow backend = "aiograpi" REPL startup without requiring a HikerAPI token.
• Sync README/docs and uv.lock metadata with the current project version.

Test Coverage

All changed code paths have regression coverage:

• setup prompt text and config writing
• legacy hiker alias normalization
• public --backend help output
• missing aiograpi dependency error hint
• aiograpi startup without HikerAPI token

Coverage gate: 82.01% total, above the 75% CI threshold.

Pre-Landing Review

No issues found. Scope is CLI/config/backend selection, docs, and tests. No SQL/data safety, LLM trust-boundary, or frontend/UI paths changed.

Eval Results

No prompt-related files changed. Evals skipped.

Plan Completion

No plan file detected.

TODOS

No TODO items completed in this PR.

Test plan

• .venv/bin/ruff check
• .venv/bin/ruff format --check
• .venv/bin/mypy insto
• .venv/bin/python -m pytest (908 passed)
• .venv/bin/python -m pytest --cov=insto --cov-fail-under=75 (908 passed, 82.01% coverage)
• uv lock --check