[Codebase Audit] Reduce panic-prone calls in `src/metrics/mod.rs`

[kelly-musk]

Problem

src/metrics/mod.rs contains 85 panic-prone calls (unwrap, expect, or panic!).

Evidence

• src/metrics/mod.rs:41 — .expect("encoding metrics failed");
• src/metrics/mod.rs:42 — String::from_utf8(buf).expect("metrics output is not valid UTF-8")
• src/metrics/mod.rs:57 — HTTP_REQUESTS_TOTAL.get().expect("metrics not initialised")
• src/metrics/mod.rs:63 — .expect("metrics not initialised")
• src/metrics/mod.rs:69 — .expect("metrics not initialised")

Proposed fix

Replace non-essential unwrap/expect usages with typed error propagation and contextual logging. Keep explicit panics only where unrecoverable invariants are well-documented.

Acceptance criteria

• All avoidable panic-prone calls in this file are removed or justified with comments/tests.
• Error paths return typed errors and preserve observability context.
• Existing tests pass (or new tests cover changed paths).

[Jokay1997]

@Jokay1997 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I would love to take on this issue. I’ve reviewed the event ingestion logic. I have an experience with Rust, Soroban smart contracts, frontend programming languages and other programming languages. Pls assign this to me

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Jokay1997 to this issue.

[KOMANIDEV]

@KOMANIDEV has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hi Maintainer, I've reviewed the issue and can replace the panic-prone calls with robust error handling, propagate typed errors with contextual logging, and preserve panics only for documented unrecoverable invariants. I'd appreciate being assigned this issue.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @KOMANIDEV to this issue.

[Pafekzy]

@Pafekzy has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hello Maintainer, I would like to work on this issue.

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[Olisachukwuma1]

@Olisachukwuma1 has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

i would like to work to on this issue

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[LiegeFx]

@LiegeFx has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hello Maintainer, I’m interested in contributing to this issue. I’ll ensure the implementation is clean, reliable, and consistent with the project guidelines.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @LiegeFx to this issue.

[Abba073]

@Abba073 has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hi maintainer, i would like to work on this issue

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[canicefavour]

@canicefavour has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

I can harden src/metrics/mod.rs by replacing recoverable unwrap/expect paths with typed error propagation and structured logging, preserving observability while documenting any truly unrecoverable invariants, and I'll add or update tests to ensure the revised error paths behave correctly without introducing regressions.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @canicefavour to this issue.