# Specification: Fix LiteFS Configuration and Process Management (`fix_litefs_config`)

## Overview
Reconfigure the Navidrome/LiteFS process management to ensure Navidrome and its Consul service registration only occur on the Primary node. This will be achieved by leveraging the LiteFS `exec` block and updating the `entrypoint.sh` logic. Additionally, correct the Navidrome database and storage paths to properly utilize the LiteFS replicated mount.

## Functional Requirements
- **LiteFS Configuration (`litefs.yml`):**
    - Enable the `exec` block to trigger `/usr/local/bin/entrypoint.sh`.
    - This allows LiteFS to manage the lifecycle of the application.
- **Entrypoint Logic (`entrypoint.sh`):**
    - Implement a supervision loop that monitors leadership via the `/data/.primary` file.
    - **On Primary:**
        - Register the node as the `navidrome` (primary) service in Consul.
        - Start the Navidrome process.
    - **On Replica:**
        - Ensure Navidrome is NOT running.
        - Deregister the `navidrome` primary service if previously registered.
        - (Optional) Register as a replica service or simply wait.
    - **On Transition:** Handle graceful shutdown of Navidrome if the node loses leadership.
- **Storage and Path Configuration (`navidrome-litefs-v2.nomad`):**
    - Set `ND_DATAFOLDER` to `/data` (the LiteFS FUSE mount).
    - Set `ND_CACHEFOLDER` to `/shared_data/cache` (shared persistent storage).
    - Set `ND_BACKUP_PATH` to `/shared_data/backup` (shared persistent storage).
- **Dockerfile Updates:**
    - Update `ENTRYPOINT` to `["litefs", "mount"]` to allow LiteFS to act as the supervisor.

## Non-Functional Requirements
- **Robustness:** Use a simple bash loop for process management to avoid extra dependencies.
- **Signal Handling:** Ensure signals (SIGTERM) are correctly forwarded to Navidrome for graceful shutdown.

## Acceptance Criteria
- [ ] Navidrome process runs ONLY on the Primary node.
- [ ] Consul service `navidrome` correctly points to the current Primary.
- [ ] Navidrome database (`navidrome.db`) is confirmed to be on the `/data` mount.
- [ ] Cluster failover correctly stops Navidrome on the old primary and starts it on the new one.

## Out of Scope
- Implementation of complex init systems like `tini` (bash loop selected by user).