[style](trx-rs): fix clippy warnings for -D warnings CI

The CI lint job runs clippy with -D warnings, which surfaced a set of
existing warnings across decoders, the client, and the soapysdr backend.
Resolve them so the workspace is clean under the enforced lint level:

- collapsible_match / identity_op / needless_range_loop / same_item_push
  in trx-rds, trx-wspr, trx-vdes, trx-wefax, trx-aprs (mostly tests)
- field_reassign_with_default -> struct-update syntax in trx-client config
  tests
- assign_op_pattern, useless vec!, and test-module ordering picked up by
  cargo clippy --fix in trx-client and the soapysdr WFM tests

No behaviour changes; all affected crates' tests pass.

Assisted-By: Claude Code (claude-opus-4)
Claude-Session: https://claude.ai/code/session_01NFpGtGTWUEYXLwZeZs2RAV
Signed-off-by: Stan Grams <sjg@haxx.space>

src/decoders/trx-wefax/src/image.rs

@@ -374,8 +374,8 @@ mod tests {
         let (y, m, d, h, mi, _) = unix_to_utc(1775055000);
         assert_eq!(y, 2026);
         // Just verify reasonable values without asserting exact date.
-        assert!(m >= 1 && m <= 12);
-        assert!(d >= 1 && d <= 31);
+        assert!((1..=12).contains(&m));
+        assert!((1..=31).contains(&d));
         assert!(h < 24);
         assert!(mi < 60);
     }

src/decoders/trx-wefax/src/phase.rs

@@ -161,10 +161,8 @@ mod tests {
 
         for line_idx in 0..20 {
             let mut line = vec![1.0f32; spl];
-            for j in pulse_start..pulse_start + pw {
-                if j < spl {
-                    line[j] = 0.0;
-                }
+            for slot in line.iter_mut().skip(pulse_start).take(pw) {
+                *slot = 0.0;
             }
             let result = det.process(&line);
             if let Some(offset) = result {