chore(deps): update base64 and syn

[josecelano]

Summary

• Update the root application's direct base64 dependency from 0.22.1 to 0.23.1.
• Update the syn dependencies used by the workspace-coupling and clippy-allow-reasons developer tools from 2.0.119 to 3.0.5.
• Refresh the affected Cargo.lock dependency edges.

Scope

• Cargo.toml and Cargo.lock
• contrib/dev-tools/analysis/workspace-coupling/Cargo.toml
• contrib/dev-tools/checks/clippy-allow-reasons/Cargo.toml

Validation

• cargo check --workspace --all-targets --all-features
• cargo test --package clippy-allow-reasons --package workspace-coupling
• cargo test --package torrust-tracker --lib --bins
• cargo fmt --check
• git diff --check
• Pre-commit hook
• Pre-push hook

Supersedes Dependabot PRs #2209 and #2055.

[Copilot]

🟢 Approval recommended

No unresolved review comments remain, and validation passed.

Pull request overview

Updates base64 and developer-tool syn dependencies, with corresponding Cargo.lock refreshes.

Changes:

• Bumps base64 to 0.23.1.
• Bumps syn to 3.0.5.
• Refreshes affected lockfile entries.

File summaries

File	Description
contrib/dev-tools/checks/clippy-allow-reasons/Cargo.toml	Updates syn.
contrib/dev-tools/analysis/workspace-coupling/Cargo.toml	Updates syn.
Cargo.toml	Updates base64.
Cargo.lock	Refreshes dependency edges.

Review details

• Files reviewed: 3/4 changed files
• Comments generated: 0
• Review effort level: Lite

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[josecelano]

ACK 6a5fc02