Feat: add server and clean some things

[Zatiji]

Changes :

• Add server module in tracel-app
• Delete tracel-macro crate
• Rename all GitHub URLs leading to Tracel products
• Add tests to JobRegister and fragment its logic
• Refactor tracel-app errors to be more organized
• Add examples for a dry-run and a server use-case

How the Server module works

The Server exposes registered jobs as POST endpoints at /{job_name}. When a request arrives, it follows a two-phase flow:

1. Validate synchronously: the JSON body is deserialized and validated via the JobRegister. If the job name is unknown → 404; if the body is invalid → 400.
2. Run asynchronously: once validated, the job is spawned on a blocking thread (spawn_blocking), and the server immediately returns 200 with the message "Job '{name}' has started running", making it a fire-and-forget dispatch. Execution errors are logged to stderr but not returned to the caller.

Jobs are registered via a builder API (Server::new().register(job)) and the server binds with Axum/Tokio.

[Marc-AnthonyG]

1. We need to trace with info the server url when it start.
2. Would be nice if the default behavior was the same as the json mapper with all field optional with default? Is this possible to do? (we need to offer both)

[Marc-AnthonyG]

Wait there is some deps that might not be cross compile compatible

[Copilot]

Pull request overview

This PR expands the Tracel SDK by introducing an optional HTTP server for dispatching registered jobs, refactors job registration/execution to support a validate-then-run flow, and removes the tracel-macros proc-macro crate while updating some repository/product links and examples.

Changes:

• Added an (feature-gated) Axum/Tokio-based server module to tracel-app, enabling fire-and-forget job execution via POST /{job_name}.
• Refactored JobRegister to split validation from execution and added unit tests for the new behavior.
• Removed tracel-macros and updated workspace/deps and release workflow accordingly; added new MNIST examples for dry-run and server usage.

Reviewed changes

Copilot reviewed 18 out of 20 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
README.md	Updates some URLs, adds new CLI link, but still contains macro-based Quick Start content that no longer matches the code.
examples/mnist/examples/mnist-server.rs	New example demonstrating Server usage with multiple jobs/defaults.
examples/mnist/examples/mnist-dry-run.rs	New example demonstrating a “dry-run” execution path.
examples/mnist/Cargo.toml	Adds server feature (and enables it by default) to compile the server example.
crates/tracel/src/lib.rs	Removes macros re-export but crate-level docs still reference macros/register.
crates/tracel/Cargo.toml	Adds a server feature that forwards to tracel-app/server.
crates/tracel-macros/src/lib.rs	Deleted proc-macro implementation for #[register].
crates/tracel-macros/Cargo.toml	Deleted crate manifest for tracel-macros.
crates/tracel-app/src/server/mod.rs	Implements the HTTP server and request handler wiring.
crates/tracel-app/src/server/error.rs	Adds ServerError and maps JobRegisterError into server-facing errors.
crates/tracel-app/src/lib.rs	Feature-gates the new server module.
crates/tracel-app/src/job.rs	Introduces erased validate/run function types used by JobRegister.
crates/tracel-app/src/job_register.rs	Splits dispatch into validate + run, adds error enum + unit tests.
crates/tracel-app/src/cli/mod.rs	Adapts CLI dispatch to the new JobRegisterError flow and renames default job field.
crates/tracel-app/src/cli/error.rs	Refactors CLI error types and adds From<JobRegisterError> mapping.
crates/tracel-app/Cargo.toml	Adds feature flags and optional deps for the server implementation.
Cargo.toml	Updates repository metadata, adds server deps, and switches tracel-client to a git dependency.
Cargo.lock	Updates lockfile for dependency/source changes (including new server-related deps).
.gitignore	Ignores .claude/ directory.
.github/workflows/publish.yml	Removes publishing steps for the deleted tracel-macros crate.

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