chore: Prune 4 transitive deps from requirements.txt

Removed MarkupSafe, rfc3986, sniffio, starlette — all pulled in
automatically as transitive dependencies of fastapi/httpx/anyio.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

requirements.txt

@@ -24,7 +24,6 @@ httpx
 idna
 # itsdangerous
 # Jinja2
-MarkupSafe
 mysqlclient
 numpy
 openpyxl
@@ -46,11 +45,8 @@ PyYAML
 qrcode
 redis[hiredis]
 requests
-rfc3986
 # six
-sniffio
 SQLAlchemy==1.4.52
-starlette
 stripe
 typing_extensions
 ujson