fix: correct config key typo and pin Invite to production DB via getConnectionName()

Reverts the two overcorrecting commits (561d3cd, 3865ec7) and replaces
them with the minimal, correct changes:

## 1. Config key typo fix (Model.php, Setting.php)

The base Model constructor and Setting constructor both used:

    $this->connection = config('fleetbase.db.connection');

The correct key is 'fleetbase.connection.db'. The wrong key returned null,
which caused $this->connection to be set to null on every instantiation,
making all models fall back to config('database.default'). In sandbox mode
that is 'sandbox', so models that explicitly declared $connection = 'mysql'
(Invite, Setting, User, Company, etc.) were silently overwritten.

Fixed to: config('fleetbase.connection.db', 'mysql')

The constructor is intentionally kept — it is the correct place to resolve
the configured production connection name for models that do not declare
their own $connection.

## 2. Invite::getConnectionName() override (Invite.php)

Invites must always be stored in and read from the production database,
regardless of sandbox mode. The $connection property alone is insufficient
because the base Model constructor overwrites it at instantiation time.

Overriding getConnectionName() is the Laravel-idiomatic way to enforce a
hard connection binding at the model level — it is called by Eloquent for
every query and cannot be overridden by runtime config changes.

Author: Ronald A Richardson

src/Models/Invite.php

@@ -38,6 +38,25 @@ class Invite extends Model
      */
     protected $connection = 'mysql';
 
+    /**
+     * Invites must always be stored in the production database.
+     *
+     * Sandbox mode switches `database.default` to `sandbox` and the base
+     * Model constructor sets `$this->connection` from config, which means
+     * any model without an explicit override would write to the sandbox DB.
+     * Overriding getConnectionName() here ensures that no matter what the
+     * runtime config state is, Invite records are always read from and
+     * written to the production connection. This is intentional: invite
+     * codes must be resolvable when the invited user accepts the link,
+     * which always happens outside of sandbox context.
+     *
+     * @return string
+     */
+    public function getConnectionName(): string
+    {
+        return config('fleetbase.connection.db', 'mysql');
+    }
+
     /**
      * These attributes that can be queried.
      *

src/Models/Model.php

@@ -30,6 +30,20 @@ class Model extends EloquentModel
     public const UUID_COLUMN      = 'uuid';
     public const PUBLIC_ID_COLUMN = 'public_id';
 
+    /**
+     * Create a new instance of the model.
+     *
+     * @param array $attributes the attributes to set on the model
+     *
+     * @return void
+     */
+    public function __construct(array $attributes = [])
+    {
+        parent::__construct($attributes);
+
+        $this->connection = config('fleetbase.connection.db', 'mysql');
+    }
+
     /**
      * The primary key for the model.
      *

src/Models/Setting.php

@@ -20,6 +20,20 @@ class Setting extends EloquentModel
     use Searchable;
     use Filterable;
 
+    /**
+     * Create a new instance of the model.
+     *
+     * @param array $attributes the attributes to set on the model
+     *
+     * @return void
+     */
+    public function __construct(array $attributes = [])
+    {
+        parent::__construct($attributes);
+
+        $this->connection = config('fleetbase.connection.db', 'mysql');
+    }
+
     /**
      * No timestamp columns.
      *