Merge torrust#839: chore!: migrate workspace to Rust edition 2024

ed58e78 feat!: migrate workspace to Rust edition 2024 (Cameron Garnham)
460f518 refactor: remove `located-error` package, use `tracing` for error context (Cameron Garnham)

Pull request description:

  ### Summary

  This PR completes two related housekeeping tasks that prepare the codebase for the next major release cycle:

  1. **Remove the `located-error` package** — The first-party `torrust-index-located-error` crate is replaced by direct `tracing::error!` calls at error-construction sites. Error types in `config` and `web::api::server` are simplified from `LocatedError<'static, dyn Error + Send + Sync>` to plain `Arc<dyn Error + Send + Sync>` (`DynError`), eliminating a lifetime parameter and unnecessary `Arc` indirection. (See ADR-T-004.)

  2. **Migrate the entire workspace to Rust edition 2024** — The edition is bumped from 2021 to 2024, the MSRV is raised from 1.83 to 1.85, and the workspace version goes from `3.1.0-develop` to `4.0.0-develop`. Key dependency upgrades include `jsonwebtoken` 9.3 → 10, `rand` 0.9 → 0.10, and the `rust-2024-compatibility` lint group is promoted from `warn` to `deny`. Import ordering across ~55 files is reformatted to edition-2024 style. (See ADR-T-005.)

  ### Breaking Changes

  - **MSRV raised to 1.85** — contributors and CI must use rustc 1.85+.
  - **Major version bump** — `4.0.0-develop` to reflect the edition change and removed package.
  - **`located-error` crate removed** — any downstream code depending on `torrust-index-located-error` must migrate to `tracing` or plain error types.

  ### Dependency Pin Status

  Most transitive pins from ADR-T-003 have been lifted thanks to the MSRV-aware resolver in edition 2024. A handful of pins remain for the `time` family and `psm` until their upstream crates support Rust 1.85 (details in ADR-T-005).

  ### Scope

  68 files changed, ~920 insertions, ~1120 deletions (net reduction). The bulk of the diff is the deleted `located-error` package, Cargo.lock churn from dependency upgrades, and mechanical import reordering by `cargo fmt`.

ACKs for top commit:
  da2ce7:
    ACK ed58e78

Tree-SHA512: 831f34cc7dc0d385d4c568fd29fb970a41cf3a343c11b14f1b5c1567d56a9a2e93b80f4a8b2efee0834a4ed2e643bcd720de414928e1f0336a736addcb9bf9ed

Author: da2ce7

CHANGELOG.md

@@ -0,0 +1,33 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+## [4.0.0] - 2026-03-23
+
+### Added
+
+- ADR-T-004: Document rationale for removing `located-error` package.
+- ADR-T-005: Document rationale for Rust edition 2024 migration.
+
+### Changed
+
+- **BREAKING:** Raise MSRV from 1.83 to 1.85.
+- **BREAKING:** Migrate workspace to Rust edition 2024.
+- **BREAKING:** Bump workspace version from `3.1.0-develop` to `4.0.0-develop`.
+- Upgrade `jsonwebtoken` from 9.3 to 10 (with `rust_crypto` feature).
+- Upgrade `rand` from 0.9 to 0.10; rename `rand::Rng` to `rand::RngExt`.
+- Promote `rust-2024-compatibility` lint group from `warn` to `deny`.
+- Reformat imports across ~55 files to edition 2024 style.
+- Simplify error types in `config` and `web::api::server` — replace
+  `LocatedError<'static, dyn Error + Send + Sync>` with `Arc<dyn Error + Send + Sync>`.
+- Emit `tracing::error!` events where `LocatedError` previously logged context.
+
+### Removed
+
+- **BREAKING:** Remove first-party `torrust-index-located-error` package
+  (`packages/located-error/`). Use `tracing` for error-origin context instead.