fix(api): coerce string booleans before persisting module_config bool values (#359)

PHP truthy semantics treat the literal `'false'` as truthy, so `$value ? 'true' : 'false'` in `setVariableValue()` persisted every 'switch off' request as `'true'` for ~30 modules with bool config variables. Canonicalise via the existing `inputToBool()` helper before the ternary so JSON.stringify(boolean) inputs land on the right storage string.

Live repro (api-v2.truckwash.io, 2026-08-10 09:25):
```
POST /minimax/config {variable:"enabled", value:"false"} → 200
GET  /minimax/config?variable=enabled → {value:true, ...}      ← unchanged
POST /minimax/config {variable:"enabled", value:false}   → 200
GET  /minimax/config?variable=enabled → {value:false, ...}     ← JSON bool works
```

Tests: `tests/Unit/MiniMax/MiniMaxEnabledSetVariableValueTest.php` (6 assertions, captures the UPDATE column value via stubbed `updateVariableValue`/`insertVariableValue` for string/boolean × true/false × insert/update paths).

Companion pleno-vue PR #281 lands the matching UI-side fix (`onMiniMaxEnabledSwitch` re-fetches + optimistic rollback).

services/nginx/app/tests/Unit/MiniMax/MiniMaxEnabledSetVariableValueTest.php

@@ -0,0 +1,103 @@
+<?php
+
+/**
+ * End-to-end regression for the bool-truthy-string bug:
+ *
+ * \traits\module_config_variable::setVariableValue() converts boolean
+ * values to the storage strings 'true' / 'false' via
+ *   `$value ? 'true' : 'false'`
+ * but PHP treats any non-empty string as truthy — including the literal
+ * 'false' that the frontend sends for an unchecked toggle
+ * (JSON.stringify(false) === "false"). Without an explicit coercion
+ * to a real bool first, the storage value flips the wrong way for every
+ * "switch off" request against every boolean config variable (~30
+ * modules).
+ *
+ * These tests call setVariableValue() against an in-memory db stub that
+ * captures the UPDATE statement's column value, so the regression is
+ * pinned at the trait level rather than at any one call site.
+ */
+
+app_require('traits/module_config_variable_t.php');
+
+use traits\module_config_variable;
+
+if (!class_exists('BoolSetVariableValueStub')) {
+    class BoolSetVariableValueStub
+    {
+        use module_config_variable;
+
+        /** @var array<int, array{string, string, mixed}> */
+        public array $updates = [];
+
+        /** @var array<int, array{string, string, mixed}> */
+        public array $inserts = [];
+
+        public bool $exists = true;
+
+        public function __construct()
+        {
+            $this->module_name = 'miniMax';
+            $this->config_variable = 'enabled';
+            $this->config_variable_type = 'bool';
+            $this->config_variable_required = true;
+            $this->config_variable_is_secret = false;
+            $this->allowed_values = null;
+        }
+
+        protected function isVariableSet(string $module, string $variable): bool
+        {
+            return $this->exists;
+        }
+
+        protected function updateVariableValue(string $module, string $variable, mixed $value): void
+        {
+            $this->updates[] = [$module, $variable, $value];
+        }
+
+        protected function insertVariableValue(string $module, string $variable, mixed $value): void
+        {
+            $this->inserts[] = [$module, $variable, $value];
+        }
+    }
+}
+
+it('stores the string "false" as "false" (the bug regressed to "true")', function (): void {
+    $stub = new BoolSetVariableValueStub();
+    $stub->setVariableValue('false');
+    expect($stub->updates)->toHaveCount(1);
+    expect($stub->updates[0][2])->toBe('false');
+});
+
+it('stores the string "true" as "true"', function (): void {
+    $stub = new BoolSetVariableValueStub();
+    $stub->setVariableValue('true');
+    expect($stub->updates)->toHaveCount(1);
+    expect($stub->updates[0][2])->toBe('true');
+});
+
+it('stores a JSON boolean false as "false"', function (): void {
+    $stub = new BoolSetVariableValueStub();
+    $stub->setVariableValue(false);
+    expect($stub->updates[0][2])->toBe('false');
+});
+
+it('stores a JSON boolean true as "true"', function (): void {
+    $stub = new BoolSetVariableValueStub();
+    $stub->setVariableValue(true);
+    expect($stub->updates[0][2])->toBe('true');
+});
+
+it('falls back to insertVariableValue when the row does not exist yet', function (): void {
+    $stub = new BoolSetVariableValueStub();
+    $stub->exists = false;
+    $stub->setVariableValue('false');
+    expect($stub->updates)->toBeEmpty();
+    expect($stub->inserts)->toHaveCount(1);
+    expect($stub->inserts[0][2])->toBe('false');
+});
+
+it('rejects int inputs for a bool config variable', function (): void {
+    $stub = new BoolSetVariableValueStub();
+    expect(fn () => $stub->setVariableValue(42))->toThrow(Exception::class);
+});

services/nginx/app/traits/module_config_variable_t.php

@@ -152,8 +152,15 @@ trait module_config_variable
         if (!$this->validateVariableValue($value)) {
             throw new Exception('Invalid value for config variable: ' . $this->config_variable . ' (' . $value . ')');
         }
-        // If the type is a boolean, convert the value to "true" or "false"
+        // If the type is a boolean, convert the value to a real boolean first.
+        // PHP's truthy semantics treat any non-empty string — including the
+        // literal 'false' — as truthy, so a naive `$value ? 'true' : 'false'`
+        // would persist the string 'false' as 'true'. The frontend sends JSON
+        // booleans as the strings 'true' / 'false', so this branch runs on
+        // every toggle. inputToBool() canonicalises both string and boolean
+        // inputs to a real bool before the ternary.
         if ($this->config_variable_type === 'bool') {
+            $value = is_string($value) ? self::inputToBool($value) : (bool)$value;
             $value = $value ? 'true' : 'false';
         }
         // Update the value of the config variable in the database, and insert it if it does not exist