Motivation:
The MULTIPLE_FEATURE_VIEW_POINT_IN_TIME_JOIN Jinja template used by the
ClickHouse offline store generated two SQL patterns ClickHouse rejects:
1. `ON TRUE` in a JOIN clause raises `INVALID_JOIN_ON_EXPRESSION` -
   ClickHouse requires a concrete predicate expression, not a bare
   boolean literal. This affected every query, single or multi
   FeatureView.
2. Chaining multiple `USING (...)` clauses across the final LEFT JOINs
   raises `Code: 48. Multiple USING statements are not supported`,
   breaking any get_historical_features() call spanning 2+
   FeatureViews.

Approach:
- Replace `ON TRUE` + unconditional `AND` chain with a conditional
  `ON`/`AND` chain over the featureview's entities. FeatureViews with
  no entities (non-entity retrieval) fall back to `ON 1 = 1`, an
  equality expression ClickHouse accepts, instead of emitting a JOIN
  with no condition at all.
- Replace the final `USING ("{{featureview.name}}__entity_row_unique_id")`
  with an explicit `ON "{{featureview.name}}"."...id" =
  entity_dataframe."...id"`, so each LEFT JOIN carries its own
  qualified predicate instead of colliding on a shared USING clause.

Both forms are standard SQL, also valid on PostgreSQL, though
postgres.py's own template is untouched since PostgreSQL already
accepts `ON TRUE` and is not affected by this bug.

Validation:
- Added TestMultipleFeatureViewPointInTimeJoinQuery to
  sdk/python/tests/unit/infra/offline_stores/test_clickhouse.py,
  rendering the real MULTIPLE_FEATURE_VIEW_POINT_IN_TIME_JOIN template
  via build_point_in_time_query() (no mocking of the template itself)
  for: two FeatureViews with entities (the reported bug), and a
  FeatureView with zero entities (the non-entity-retrieval edge case
  the fix also has to preserve).
- Confirmed both new tests FAIL against the pre-fix template (still
  emit `ON TRUE` / colliding `USING`) and PASS against the post-fix
  template - a failing-then-passing reproduction of the reported
  defect, run via `uv run pytest
  sdk/python/tests/unit/infra/offline_stores/test_clickhouse.py -v`.
- Ran `uv run ruff check` and `uv run ruff format --check` on both
  changed files (pass), and `mypy` on the changed source file (pass,
  via `uv run bash -c "cd sdk/python && mypy
  feast/infra/offline_stores/contrib/clickhouse_offline_store/clickhouse.py"`).
- Could not run against a live ClickHouse instance or the repo's
  broader `make test-python-unit` / full mypy sweep in this
  environment (no Docker/ClickHouse available locally, and several
  unrelated contrib offline stores require optional extras this
  environment doesn't have installed); the defect here is a SQL
  syntax incompatibility visible directly in the rendered template
  output, so the failing-to-passing unit test is a direct
  reproduction of it.

Report: feast-dev#6141
Signed-off-by: Pujitha Paladugu <10557236+pujitha24@users.noreply.github.com>
Assisted-by: claude-sonnet-5 (via Claude Code)

The new test class added earlier in test_clickhouse.py shifted the
existing password="password" placeholder down to line 83, which the
detect-secrets pre-commit hook flagged as a stale baseline entry.

Signed-off-by: Pujitha Paladugu <10557236+pujitha24@users.noreply.github.com>