Remove surrounding whitespace before processing query

Ran into this issue twice quite by accident with fat-fingering copy/paste on
my phone. If there is any whitespace in front of or trailing after the
lookup query, it returns an "Unexpected error". Stripping the string is the
quick and dirty way to clean it.

I hate modifying the same function argument name in place like that, but it
is valid Python. If you want me to assign it to a separate variable and
replace all the references of "query", let me know.

Thanks!

app/lookup.py

@@ -10,6 +10,7 @@ from app.source import _MENTION_REGEX
 
 
 async def lookup(db_session: AsyncSession, query: str) -> Actor | RemoteObject:
+    query = query.strip()
     if query.startswith("@") or _MENTION_REGEX.match("@" + query):
         query = await webfinger.get_actor_url(query)  # type: ignore  # None check below