feat: Reinit server with token on demand, enable reusing exisitng configuration in all modes, update error output

[vonjackets]

This fix is tied to the issue I opened (#209), below is a review of what I aim to solve here.
Please let me know if this belongs in a renovate/ branch!

Problem Analysis

Panic when running in other modes without configuration

I noticed this when playing with attic, trying to run in api-server mode with no config panicked every time.

• Scenario: Running atticd --api-server without a pre-existing configuration file causes a panic.
• Root Cause: The run_oobe function, responsible for generating default configurations and tokens, is bypassed when the server is executed in API Server mode, leaving the server in an undefined state.
• Impact: This prevents the server from starting properly in a default configuration, blocking administrators from easily deploying the API Server.

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Missing Root Token in Monolithic Mode with Pre-Existing Configuration

• Scenario: When the server is run in Monolithic Mode with a configuration file that includes an RS256 key, the run_oobe function is skipped. This prevents a root token from being generated.

• Root Cause: The logic incorrectly assumes that the presence of a configuration file implies a fully initialized server, bypassing critical token generation steps.

• Impact:

  1. Authentication Failure: Administrators cannot authenticate to the server because no root token is created.
  2. Operational Failure: atticadm generates "do-nothing" tokens, effectively rendering it non-functional.
  3. Deployment Inconsistency: The behavior creates discrepancies between first-run and subsequent runs of the server.

  So far, my testing has consisted of trying to work through my desired use case of using this for ci/cd builds. I intend to try deploying this fix within a container and running it there with a sqlite db.

  I have also ran the nix build . command from the root to ensure the entire project can be recreated. Please let me know if there's other work/testing output you'd like to see!