Sweep the pinned toolchain to Rust 1.97

The Windows UI needs current winsafe, whose real minimum is 1.89 (its manifest
under-declares 1.87 while it uses NonNull::from_ref). Rather than stop at the
minimum, this goes to current stable and fixes what that costs.

The counter-intuitive result: 1.97 is CHEAPER than 1.89. libfreemkv had 54
clippy errors at 1.89 and 6 at 1.97, because clippy tightened the noisy
collapsible_if lint in between. Stopping at the minimum would have been the most
expensive choice available.

Roughly 47 lints across the eight repos, the large majority auto-fixed:
libfreemkv 6, freemkv-engine 14, bdemu 8, freemkv-keysources 7, autorip 6,
freemkv-unlock 3, freemkv-i18n 3. The hand-fixed ones are a descending sort to
sort_by_key(Reverse), four manual checked-division sites, a loop counter replaced
by enumerate, and a loop whose first let-else became a while-let.

Worth recording for whoever bumps next: clippy is MSRV-AWARE. Those 54 lints only
appear once the crate DECLARES 1.89 or later, because let-chains become
available. A bare `cargo +1.89 clippy` against a manifest still pinned at 1.87
reports clean and is meaningless — gate with the real precommit script, which is
also the only thing that covers build scripts.

The pin still sits below the Mac default, so it keeps doing its job: catching
lint drift locally before CI sees it.

Cargo.toml

@@ -2,7 +2,7 @@
 name = "freemkv-unlock"
 version = "1.6.0"
 edition = "2024"
-rust-version = "1.87"
+rust-version = "1.97"
 license = "MIT"
 description = "Unlock layer for the freemkv toolchain: the Unlocker contract + self-contained firmware/AACS/CSS unlocker modules. libfreemkv depends on this and dispatches via all_unlockers()."
 repository = "https://github.com/freemkv/freemkv-unlock"

src/ld/profile.rs

@@ -141,7 +141,7 @@ pub struct ProfileMatch {
 /// translatable English message.
 fn decode_hex(s: &str) -> std::result::Result<Vec<u8>, &'static str> {
     let bytes = s.as_bytes();
-    if bytes.len() % 2 != 0 {
+    if !bytes.len().is_multiple_of(2) {
         return Err("hex");
     }
     let mut out = Vec::with_capacity(bytes.len() / 2);
@@ -304,19 +304,19 @@ pub fn find_by_drive_id(profiles: &Profiles, drive_id: &crate::DriveId) -> Optio
         (Platform::Mt1959B, &profiles.mt1959_b),
         (Platform::Renesas, &profiles.renesas),
     ] {
-        if !prod.is_empty() {
-            if let Some(p) = list.iter().find(|p| {
+        if !prod.is_empty()
+            && let Some(p) = list.iter().find(|p| {
                 p.identity.vendor_id.trim() == v
                     && p.identity.product_id.trim() == prod
                     && p.identity.product_revision.trim() == r
                     && p.identity.vendor_specific.trim() == vs
                     && p.identity.firmware_date.trim() == date
-            }) {
-                return Some(ProfileMatch {
-                    profile: p.clone(),
-                    platform,
-                });
-            }
+            })
+        {
+            return Some(ProfileMatch {
+                profile: p.clone(),
+                platform,
+            });
         }
 
         if let Some(p) = list.iter().find(|p| {