Recognize JOIN before parenthesized subqueries

[adenzhou1350]

JOIN(SELECT ...) is currently consumed by the function-name lookahead. As a
result, child join(...) as p becomes a single Identifier instead of a table,
JOIN keyword and subquery alias.

Move the existing JOIN regex ahead of that lookahead, keeping it after the dotted
name guards. The regression covers bare and compound JOINs, subquery aliases,
unchanged SQL text, ordinary function names and schema.join(...).

Refs #615's JOIN example; this does not change UNNEST or ANY classification.

Validation on Windows / Python 3.14.3 / pytest 9.0.3:

• Final regressions: unchanged source has 2 failures and 8 passing controls;
  patched source passes all 10.
• Full upstream suite: 516 passed, 2 xfailed, 1 xpassed. The xfail/xpass outcomes
  also occur on the unchanged-source baseline.
• ruff check sqlparse/ tests/test_join_parenthesis.py and git diff --check pass.
• All six subquery JOIN statements also execute successfully against in-memory
  SQLite 3.50.4; no cross-dialect qualification is claimed.

Prepared with AI assistance.

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