style: crank clippy to pedantic+nursery and fix all lints

Enable the full clippy all + pedantic + nursery groups as workspace warnings,
with a small documented allow-list for the pedantic/nursery lints this project
intentionally does not follow (rustdoc-style requirements, deliberate numeric
casts in the protocol/UI layers, and a few noisy nursery lints). Also enable
the rust unused_lifetimes and unsafe_op_in_unsafe_fn lints.

Fixed every resulting warning (527 -> 0) mechanically per clippy's suggestions:
inline format args, const fns, item ordering, let-else, redundant clones,
map_or, cast_lossless, Eq derives, associated-fn conversions for methods that
never used self, and removing unnecessary Result wrappers whose call sites could
never propagate an error. No runtime behavior changed; cargo fmt applied.

cargo clippy --workspace --all-targets: 0 warnings. All tests pass.

soulseek-rs-lib/src/utils/md5.rs

@@ -22,7 +22,7 @@ use std::convert::TryInto;
 * K[i] = floor(2^32 * abs(sin(i+1)))
 */
 fn table_construction_function(i: u32) -> u32 {
-    let x: f64 = i as f64;
+    let x: f64 = f64::from(i);
     let sin_eval = x.sin().abs();
     // note: 4294967296 == 2^32
     (4294967296.0 * sin_eval) as u32
@@ -36,19 +36,19 @@ fn table_construction_function(i: u32) -> u32 {
 * algorithm, and they are performed a number of times to end
 * up with our final result.
 */
-fn f(x: u32, y: u32, z: u32) -> u32 {
+const fn f(x: u32, y: u32, z: u32) -> u32 {
     x & y | !x & z
 }
 
-fn g(x: u32, y: u32, z: u32) -> u32 {
+const fn g(x: u32, y: u32, z: u32) -> u32 {
     x & z | y & !z
 }
 
-fn h(x: u32, y: u32, z: u32) -> u32 {
+const fn h(x: u32, y: u32, z: u32) -> u32 {
     x ^ y ^ z
 }
 
-fn i(x: u32, y: u32, z: u32) -> u32 {
+const fn i(x: u32, y: u32, z: u32) -> u32 {
     y ^ (x | !z)
 }
 
@@ -67,7 +67,7 @@ fn vec_to_array<T, const N: usize>(v: Vec<T>) -> [T; N] {
 * table[i] is an entry generated by our sine function, s is an unsigned
 * integer, and a,b,c,d are our 32 bit registers we perform operations on.
 */
-fn round_one_operations(
+const fn round_one_operations(
     mut a: u32,
     mut b: u32,
     mut c: u32,
@@ -115,7 +115,7 @@ fn round_one_operations(
 * Round 2 is equivalent to round 1, except we swap out our f function for g as such:
 * a = b + ((a + g(b,c,d) + x[k] + table[i]) <<< s);
 */
-fn round_two_operations(
+const fn round_two_operations(
     mut a: u32,
     mut b: u32,
     mut c: u32,
@@ -161,7 +161,7 @@ fn round_two_operations(
 * Round 3 is equivalent to round 1, except we swap out our f function for h as such:
 * a = b + ((a + h(b,c,d) + x[k] + table[i]) <<< s);
 */
-fn round_three_operations(
+const fn round_three_operations(
     mut a: u32,
     mut b: u32,
     mut c: u32,
@@ -207,7 +207,7 @@ fn round_three_operations(
 * Round 4 is equivalent to round 1, except we swap out our f function for h as such:
 * a = b + ((a + i(b,c,d) + x[k] + table[i]) <<< s);
 */
-fn round_four_operations(
+const fn round_four_operations(
     mut a: u32,
     mut b: u32,
     mut c: u32,
@@ -287,7 +287,7 @@ fn compute_md5_digest(mut v: Vec<u8>) -> String {
     let table = construct_value_table();
 
     // let M[0 .. N-1] = words of resulting message, where N is multiple of 16
-    for chunk in v.chunks_exact_mut(64) {
+    for chunk in v.as_chunks_mut::<64>().0 {
         let x = convert_u8_chunk_to_u32(chunk);
 
         // set all values of a,b,c,d to aa,bb,cc, and dd respectively.
@@ -378,7 +378,7 @@ fn bit_padding(input: &str) -> Vec<u8> {
     input_vector
 }
 
-fn split_u64_to_u8_array(s: u64) -> [u8; 8] {
+const fn split_u64_to_u8_array(s: u64) -> [u8; 8] {
     [
         s as u8,
         (s >> 8) as u8,
@@ -425,6 +425,7 @@ fn convert_str_to_vec(input: &str) -> Vec<u8> {
 *    during our bitwise operations to retrieve our message digest.
 *    (This is a simplification, but describes the core functionality)
 */
+#[must_use]
 pub fn md5(input: &str) -> String {
     let input_vec = bit_padding(input);
     compute_md5_digest(input_vec)
@@ -454,7 +455,7 @@ fn lowercase_alphabet_correct_hash() {
     assert_eq!(
         "c3fcd3d76192e4007dfb496cca67e13b",
         md5("abcdefghijklmnopqrstuvwxyz")
-    )
+    );
 }
 
 #[test]