feat(writes): add update_wellness_bulk and update_sport_settings

update_wellness_bulk writes many days in one PUT to /wellness-bulk; the
snake_case->camelCase mapping is extracted into a shared _wellness_payload helper
so single and bulk can't drift, and the whole batch is rejected if any date is
invalid (no partial writes).

update_sport_settings changes FTP/LTHR/pace/zones with a dual guardrail: a warning
docstring, a native ctx.elicit() confirmation on capable clients, and a hard
confirm=True fallback that refuses the write (returning the old->new diff) on
clients without elicitation. It read-modify-writes the full record and passes the
spec-required recalcHrZones query param. Widened the HTTP client's data type to
accept the bulk array.

Implements #5.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NGzHtDvJur9U7ysgRKRUTN

src/intervals_mcp_server/api/client.py

@@ -154,7 +154,7 @@ async def make_intervals_request(
     api_key: str | None = None,
     params: dict[str, Any] | None = None,
     method: str = "GET",
-    data: dict[str, Any] | None = None,
+    data: dict[str, Any] | list[Any] | None = None,
 ) -> dict[str, Any] | list[dict[str, Any]]:
     """
     Make a request to the Intervals.icu API with proper error handling.