Enable clippy::panic lint #91

What this lint catches

clippy::panic warns on any explicit panic!() call in non-test production code. Panics that reach users produce cryptic crash output and bypass the crate's anyhow-based error propagation. This lint enforces that every failure path is either returned as an Err or, when a code path is genuinely unreachable, expressed with unreachable!() — which is semantically precise and excluded from this lint.

Why it improves code quality

This codebase already forbids dbg! and todo! to prevent debug artefacts from shipping. clippy::panic closes the analogous gap for accidental panics:

• Explicitness — unreachable!() signals intent (this arm cannot be reached), while panic!() is ambiguous.
• Consistency — matches the existing spirit of dbg_macro = "deny" and todo = "deny".
• Error hygiene — keeps all error paths routed through anyhow::Result and out of crash-and-burn territory.

Current state

No violations exist in production code. Test files use panic!() in match fallback arms that are genuinely unreachable; those are fixed by replacing them with unreachable!().

This issue was opened by the Clippy lint improvements → issue + PR (Rust repos) → Slack routine of moadim. CC @tupe12334