fix(pdf): enforce the per-team cap inside both by-reference placement functions (#4418)

* fix(pdf): enforce the per-team cap inside both by-reference placement functions

The rewrite (server-side GCS copy of a fire-engine handoff) and the
streaming upload trusted their callers to have applied
largePdfLimitBytes; only the router's gates enforced it. Both now
refuse over-cap inputs themselves and return null, so an oversized
file follows the pre-by-reference oversized path regardless of which
caller asked.

* test(pdf): pin cap configs explicitly and clean up the upload temp file

Addresses cubic review: the cap-enforcement block now sets both tier
caps itself instead of relying on schema defaults (and derives the
test sizes from them), and the upload-accept test unlinks its temp
file.