fix(security): port the RNG onto the rand 0.10 API

[InstaZDLL]

main does not compile. It has not since #133 merged, six hours before
#137 landed on top of it.

error[E0432]: unresolved imports `rand::rngs::OsRng`, `rand::RngCore`
  --> src/security.rs:14:12

rand 0.10 renamed OsRng to SysRng and dropped RngCore from the root.
src/security.rs is the crate's only user of either.

Commit	CI (Rust)
7168b3b — before the bump	success
2bddbdd — the rand bump	failure
0e6b80a — the module split	failure

The split's own branch was green: it forked from 869c881, before the bump,
and was never rebased. A green PR and a red base merged into a red main.

The change

SysRng is fallible where OsRng panicked internally. The three callers that
already return Result<_, SecurityError> — the instance key, the AEAD nonce and
the Argon2 salt — now report a new SecurityError::Random instead of aborting
the process. generate_token keeps its infallible signature, and therefore the
panic it already had; a system CSPRNG that will not answer leaves nothing to
retry, and drawing a token from anything else would be worse than drawing none.

SysRng rather than the infallible ThreadRng, which would have been a smaller
diff: the original asked the operating system directly, and an instance key that
outlives every other secret is the last place to start going through a userspace
buffer instead.

Gates

cargo fmt --all --check, cargo clippy --all-targets --all-features -D warnings,
42 unit and 46 integration tests — all green, which is more than main can say.

Summary by CodeRabbit

• Améliorations
  • Renforcement de la génération aléatoire utilisée pour les clés, nonces et sels de mots de passe.
  • Les échecs de génération aléatoire sont désormais signalés explicitement par une erreur de sécurité.
  • La génération de jetons gère explicitement les défaillances critiques du générateur aléatoire système.

[coderabbitai]

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• src/security.rs

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📝 Walkthrough

Walkthrough

Le module src/security.rs remplace OsRng par SysRng. Il centralise le remplissage aléatoire dans fill_random, ajoute SecurityError::Random et adapte la propagation des erreurs pour les clés, les nonces, les sels et les jetons.

Changes

Aléa cryptographique

Layer / File(s)	Summary
Contrat d’erreur et remplissage aléatoire src/security.rs	SecurityError::Random représente l’échec du CSPRNG système. fill_random utilise SysRng::try_fill_bytes et convertit cet échec en erreur de sécurité.
Propagation vers les opérations de sécurité src/security.rs	La génération de clés d’instance, de nonces et de sels propage l’erreur aléatoire. generate_token conserve une API infallible et panique explicitement en cas d’échec.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 690e7

This localized security update ports random-number generation to the rand 0.10 API and preserves the existing caller behavior while reporting failures where signatures allow it; no actionable merge-blocking risk remains after normal checks and review.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	Docstring check was indeterminate for this PR — some files could not be analyzed in time. Not blocking.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	Le titre décrit clairement la correction principale de l’intégration RNG avec rand 0.10.
Description check	✅ Passed	La description présente le problème, les changements et les validations effectuées, malgré l’absence des rubriques exactes du modèle.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/rand-0.10-api

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