Remove lint exemptions from infrastructure crates

[shahan-khatchadourian-anchorage]

Summary

Remove TODO(#231) crate-level #![allow] exemptions from non-chain infrastructure crates.

Scope

Crate	Violations	Pattern
parser_app	~12	CLI arg parsing expect(), signal handlers, borsh serialization
parser_grpc_server	~2	Ephemeral key load, reflection service init
parser_gateway	~1	SIGTERM handler registration
metrics	~5 lib, ~8 test	Metric static expect(), server bind, test setup
integration	~27	Test infrastructure — process spawning, client setup
examples	~5	Demo binary
generated	3	Auto-generated protobuf code — may need codegen template changes

Most violations are expect() in startup/init code where crashing is arguably acceptable (can't serve if you can't bind a port). These can either be converted to proper error propagation or given per-line #[allow] with a justification comment.

Depends on

• Adopt workspace-level clippy lint denials from tvc-template #231 / PR feat: adopt workspace-level clippy lint denials #245

[shahan-khatchadourian-anchorage]

For implementation patterns, see PR #245 as a reference: per-line #[allow] with comments for infallible cases, #[allow] on test modules, .unwrap() → ? for fallible paths, panic! → Err(...) for error propagation.