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/service/migrations.rs

@@ -215,8 +215,8 @@ async fn db_lt_12(services: &Services) -> Result<()> {
 	for username in &services
 		.users
 		.list_local_users()
-		.map(UserId::to_owned)
-		.collect::<Vec<_>>()
+		.map(ToOwned::to_owned)
+		.collect::<Vec<OwnedUserId>>()
 		.await
 	{
 		let user = match UserId::parse_with_server_name(username.as_str(), &services.server.name)
@@ -295,8 +295,8 @@ async fn db_lt_13(services: &Services) -> Result<()> {
 	for username in &services
 		.users
 		.list_local_users()
-		.map(UserId::to_owned)
-		.collect::<Vec<_>>()
+		.map(ToOwned::to_owned)
+		.collect::<Vec<OwnedUserId>>()
 		.await
 	{
 		let user = match UserId::parse_with_server_name(username.as_str(), &services.server.name)