chore: bump Rust edition to 2024 and apply cargo fix + clippy updates

[Saul-STFC]

Run cargo fix --edition and resolve resulting warnings:

• Add use<> syntax to impl Trait return types (auto-fixed)
• Fix Rust 2024 temporary drop order changes across async main tasks and backend helpers
  • Unnest nested Ok(Json(...)) block in user-info endpoint to isolate temporary lifetimes
  • Rewrite immediate let bindings to use ? followed by explicit Ok(...) returns
  • Fix Rust 2024 temporary drop order change by simplifying _initial_reconcile_rx handling
• Apply Clippy suggestions
  • Use && let chaining instead of nested if let blocks in controller.rs
    Part of Bump our Rust code to 2024 edition issues#832

Description

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Definition of Done Checklist

• Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant
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Author

• Changes are OpenShift compatible
• CRD changes approved
• CRD documentation for all fields, following the style guide.
• Helm chart can be installed and deployed operator works
• Integration tests passed (for non trivial changes)
• Changes need to be "offline" compatible
• Links to generated (nightly) docs added
• Release note snippet added

Reviewer

• Code contains useful comments
• Code contains useful logging statements
• (Integration-)Test cases added
• Documentation added or updated. Follows the style guide.
• Changelog updated
• Cargo.toml only contains references to git tags (not specific commits or branches)

Acceptance

• Feature Tracker has been updated
• Proper release label has been added
• Links to generated (nightly) docs added
• Release note snippet added
• Add type/deprecation label & add to the deprecation schedule
• Add type/experimental label & add to the experimental features tracker