[FEATURE] Consolidate CLI and web server into the aura entrypoint #409

Outcome

AURA ships one primary executable. The aura binary keeps CLI/chat behavior as its default and can launch the standalone web server through an explicit mode.

Scope

• Move the web-server entry point behind aura --webserver or the final agreed command shape.
• Share configuration loading, logging, version reporting, and startup behavior between modes.
• Preserve the existing web-server functionality and operational controls.
• Remove duplicated executable wiring and build configuration where practical.
• Update automated tests to cover both entry modes from the unified binary.

Acceptance criteria

• aura without the web-server option retains the documented CLI/chat behavior.
• The unified binary can launch the standalone web server with equivalent supported behavior.
• Both modes report the same product version and consume compatible configuration.
• Release artifacts and package work can distribute the unified binary without requiring a second executable.

Parent epic: #353
Initiative: #370