chore(workspace): fix all clippy warnings in test code

Resolves 15 violations found by `cargo clippy --workspace --tests -D warnings`:
- Remove unused imports (Card, Rank) in cursor_plugin tests
- Replace absurd i32::MAX comparison with a meaningful >= 0 check
- Use range .contains() instead of manual >= && <= (manual_range_contains)
- Move impl FromRequestParts before test module in middleware.rs (items_after_test_module)
- Move _VEC3_REFERENCED const before test module in input_plugin.rs
- Convert runtime assert on constant to const { assert!(...) }
- Use .contains() instead of .iter().any() for slice membership
- Replace .get(...).is_none() with !.contains_key(...) in HashMap checks
- Collapse Default::default() + field assignment into struct literal initializers
  across solitaire_sync, solitaire_data, and solitaire_engine test helpers

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

solitaire_data/src/progress.rs

@@ -148,8 +148,7 @@ mod tests {
 
     #[test]
     fn add_xp_saturates_on_overflow() {
-        let mut p = PlayerProgress::default();
-        p.total_xp = u64::MAX - 5;
+        let mut p = PlayerProgress { total_xp: u64::MAX - 5, ..Default::default() };
         p.add_xp(100);
         assert_eq!(p.total_xp, u64::MAX);
     }