fix: cast cached post count to int and align local cache default to redis

Production crashed on every Inertia request after the PostHog branch
landed:

  TypeError: App\Models\Account::cachedPostCount(): Return value must
  be of type int, string returned at app/Models/Traits/HasUsage.php:80

Root cause: Laravel's RedisStore optimises is_numeric values by storing
them raw (not serialised) so they remain INCR/DECR-able atomically.
The side effect is that an int written via Cache::put comes back as a
string on read. The strict ': int' return type on cachedPostCount then
threw a TypeError.

Local dev and CI used the file/array/database drivers respectively,
which serialise everything blindly and preserve the int type, so the
bug never surfaced before deploy.

Fixes:
- Cast the Cache::remember result to (int) — defensive, survives any
  driver-specific behaviour. Documented inline so the cast is not
  later removed as redundant.
- Change config/cache.php default from 'database' to 'redis' so local
  dev matches prod by default and similar driver-specific bugs surface
  before merge instead of after deploy.
- Regression test that seeds the cache with a literal string (mimics
  the production Redis read) and asserts cachedPostCount still returns
  an int.

app/Models/Traits/HasUsage.php

@@ -66,6 +66,15 @@ public function featureLimits(): array
     }
 
     /**
+     * The `(int)` cast on the cached value is load-bearing: Laravel's
+     * RedisStore skips serialize()/unserialize() for is_numeric values so
+     * they can be incremented atomically — the side effect is that an int
+     * stored via `Cache::put` comes back as a string on read. Without the
+     * cast, the strict `: int` return type throws a TypeError under the
+     * Redis cache driver (production). File/array/database drivers don't
+     * have this optimisation and preserve the type, which is why the bug
+     * never surfaced in tests or local dev.
+     *
      * @param  array<int, string>  $workspaceIds
      */
     private function cachedPostCount(array $workspaceIds): int
@@ -74,7 +83,7 @@ private function cachedPostCount(array $workspaceIds): int
             return 0;
         }
 
-        return Cache::remember(
+        return (int) Cache::remember(
             "account:{$this->id}:posts_count",
             self::POST_COUNT_CACHE_TTL,
             fn () => Post::whereIn('workspace_id', $workspaceIds)->count(),

config/cache.php

@@ -17,7 +17,7 @@
     |
     */
 
-    'default' => env('CACHE_STORE', 'database'),
+    'default' => env('CACHE_STORE', 'redis'),
 
     /*
     |--------------------------------------------------------------------------

tests/Feature/Models/HasUsageTraitTest.php

@@ -104,3 +104,22 @@
     // No cache entry should be written for the empty case.
     expect(Cache::has("account:{$this->account->id}:posts_count"))->toBeFalse();
 });
+
+test('postCount survives a string-typed cache value (Redis serializer quirk)', function () {
+    // Laravel's RedisStore stores numeric values raw (not serialised) so they
+    // can be INCRemented atomically. The side effect: an int written via
+    // Cache::put comes back as a string on read. The test driver is `array`
+    // which preserves type, so we seed the cache with a literal string here
+    // to mimic what production sees and assert the return type stays int.
+    Workspace::factory()->create([
+        'account_id' => $this->account->id,
+        'user_id' => $this->owner->id,
+    ]);
+
+    Cache::put("account:{$this->account->id}:posts_count", '42', 300);
+
+    $usage = $this->account->usage();
+
+    expect($usage['postCount'])->toBe(42);
+    expect($usage['postCount'])->toBeInt();
+});