fix: Resolve Clippy CI failures from elided lifetime warnings

The latest Rust nightly compiler (2025-08-27) introduced the
elided-named-lifetimes lint which causes Clippy CI checks to fail
when an elided lifetime ('_) resolves to a named lifetime that's
already in scope.

This commit fixes the Clippy warnings by:
- Making lifetime relationships explicit where 'a is already in scope
- Keeping elided lifetimes ('_) in functions without explicit
  lifetime parameters
- Ensuring proper lifetime handling in the database pool module

Affected files (17 total):
- Database map modules: Handle, Key, and KeyVal references in get,
  qry, keys, and stream operations
- Database pool module: into_recv_seek function

This change resolves the CI build failures without changing any
functionality, ensuring the codebase remains compatible with the
latest nightly Clippy checks.

src/database/pool.rs

@@ -443,7 +443,7 @@ pub(crate) fn into_send_seek(result: stream::State<'_>) -> stream::State<'static
 	unsafe { std::mem::transmute(result) }
 }
 
-fn into_recv_seek(result: stream::State<'static>) -> stream::State<'_> {
+fn into_recv_seek(result: stream::State<'static>) -> stream::State<'static> {
 	// SAFETY: This is to receive the State from the channel; see above.
 	unsafe { std::mem::transmute(result) }
 }