feat: add team conference and division static data

[madhavcodez]

What

Adds two static lookups for NBA team alignment and four helpers to query them.

• data.team_conferences: team_id -> "East" | "West" (30 NBA teams)
• data.team_divisions: team_id -> "Atlantic" | "Central" | "Southeast" | "Northwest" | "Pacific" | "Southwest"
• static.teams.get_team_conference(team_id)
• static.teams.get_team_division(team_id)
• static.teams.find_teams_by_conference(conference) (case-insensitive)
• static.teams.find_teams_by_division(division) (case-insensitive)

WNBA teams are intentionally excluded, matching how get_wnba_teams() is already kept separate.

Why

stats/library/parameters.py already defines Conference and DivisionSimple, but those are input enums for endpoint query params, not a way to ask "which conference is this team in?". There is no existing path from a team_id to its conference or division without hardcoding it in user code.

This fills that gap with the same shape as the existing get_team_by_id / find_teams_by_* helpers, so it reads as a natural extension rather than a new surface.

The string values are deliberately aligned with the param enums, so a typical chain works without remapping:

from nba_api.stats.static import teams
from nba_api.stats.endpoints import leaguestandings

conf = teams.get_team_conference(1610612747)  # Lakers -> "West"
standings = leaguestandings.LeagueStandings(conference_nullable=conf)

Maintenance

NBA conference/division alignment has been stable since the 2004-05 realignment, so this is effectively static reference data with no expected churn.

Tests

14 new unit tests in tests/unit/stats/static/test_static_data.py covering:

• both dicts contain all 30 NBA team ids
• values are restricted to the valid conference/division strings
• conference/division lookups for 6 known teams (parametrized)
• helpers return None for unknown ids (NBA and WNBA)
• find_teams_by_* is case-insensitive and returns the right counts (15/15 by conference, 5 per division)
• East/West sets are disjoint and together cover all 30 NBA team ids (catches a swap that count-only tests would miss)
• Pacific division has the expected {GSW, LAC, LAL, PHX, SAC} membership
• division names passed to the conference helper (and vice versa) return [] rather than silently matching
• falsy input (None, "") is tolerated rather than raising

Full suite: 534 passing locally. The 2 pre-existing tests/unit/live/endpoints/test_get_request_url failures (stale 2021 game id) reproduce on master and are unrelated, as noted in #671 and #676. ruff check and ruff format --check are clean.

Scope

No changes to endpoints, parameters, HTTP layer, or existing helpers. Additive only.

[madhavcodez]

CI failures are the same pre-existing test_get_request_url cases in tests/unit/live/endpoints/ that hit the live CDN with a stale 2021 game ID. They fail identically on master and were called out in #671 and #676 as unrelated. This PR is additive static data + helpers + tests in stats/static/stats/library — no live endpoints touched.

Local pytest tests/unit/ → 534 passed, same 2 failures. ruff check and ruff format --check clean.