fix(rust): enforce lint on all files + fix lint issues

[81reap]

Addresses most of the issues in #1389 by enabling linting on all files. Remaining issues can be fixed with mutants.rs (out of scope for this change).

Repeated PAtterns

Lint	Sites	Before	After
unused_qualifications	81	outfile: &mut impl std::io::Write	impl Write
unreachable_pub	42	pub fn inside a private module	pub(crate) fn
elided_lifetimes_in_paths	24	args: &[PathAndJson]	&[PathAndJson<'_>]
clippy::uninlined_format_args	7	format!("http://127.0.0.1:{}", port)	format!("http://127.0.0.1:{port}")
clippy::format_push_string	5	msg.push_str(&format!("Actual: {}\n", actual))	writeln!(msg, "Actual: {actual}")

One or Two Offs

Lint	Where	Change
clippy::unused_async	tests/oidc	FakeOidcProvider::new is no longer async; 4 call sites drop .await
clippy::needless_pass_by_value	tests/common	build_echo_response(body: Vec<u8>) → &[u8]
clippy::manual_assert ×2	build.rs, tests/sql_test_files	if c { panic!(..) } → assert!(!c, ..)
clippy::unnecessary_debug_formatting ×2	build.rs, src/main.rs	{path:?} → path.display()
clippy::items_after_statements	build.rs	take_between moved out of extract_icons_from_sprite to module scope
clippy::manual_let_else	tests/sql_test_files	match row.as_object() { Some(o) => o, None => continue } → let Some(obj) = .. else { continue }
clippy::map_unwrap_or	tests/oidc	.map(f).unwrap_or_else(g) → .map_or_else(g, f)
clippy::redundant_closure	tests/sql_test_files	.map(|d| d.to_string()) → .map(ToString::to_string)
clippy::explicit_iter_loop ×2	tests/core, tests/oidc	for x in v.into_iter() → for x in v; .iter() → &v
clippy::single_char_pattern	tests/data_formats	contains("{") → contains('{')
clippy::unreadable_literal ×2	tests/requests, tests/uploads	123454 → 123_454
clippy::semicolon_if_nothing_returned	tests/requests	) → );
Duration unit readability	tests/oidc	Duration::from_secs(60) → Duration::from_mins(1)
clippy::dbg_macro	src/webserver/routing.rs	deleted dbg!(&normalized_path, &self.contents) from the test file store