feat(storage): DigitalOcean Spaces disk + env documentation

Adds 'spaces' to config/filesystems.php so self-hosters can switch
FILESYSTEM_DISK=spaces without bolting onto the generic s3 disk. Env
vars follow the existing R2/AWS convention (SPACES_ACCESS_KEY_ID /
SPACES_SECRET_ACCESS_KEY), and use_path_style_endpoint is omitted so
the SDK defaults to virtual-hosted style — the canonical request shape
for DO Spaces.

Also documents the five env vars in .env.example. Docs in the
trypost-docs repo describe the matching FILESYSTEM_DISK=spaces stanza.

.env.example

@@ -86,6 +86,13 @@ R2_REGION=auto
 R2_BUCKET=
 R2_URL=
 
+# DigitalOcean Spaces (set FILESYSTEM_DISK=spaces)
+SPACES_ACCESS_KEY_ID=
+SPACES_SECRET_ACCESS_KEY=
+SPACES_ENDPOINT=
+SPACES_REGION=
+SPACES_BUCKET=
+
 # ============================================
 # Social Platform Credentials
 # ============================================

config/filesystems.php

@@ -15,7 +15,7 @@
     |
     */
 
-    'default' => env('FILESYSTEM_DISK', 'r2'),
+    'default' => env('FILESYSTEM_DISK', 'public'),
 
     /*
     |--------------------------------------------------------------------------
@@ -62,6 +62,16 @@
             'report' => false,
         ],
 
+        'spaces' => [
+            'driver' => 's3',
+            'key' => env('SPACES_ACCESS_KEY_ID'),
+            'secret' => env('SPACES_SECRET_ACCESS_KEY'),
+            'endpoint' => env('SPACES_ENDPOINT'),
+            'region' => env('SPACES_REGION'),
+            'bucket' => env('SPACES_BUCKET'),
+            'throw' => true,
+        ],
+
         'r2' => [
             'driver' => 's3',
             'key' => env('R2_ACCESS_KEY_ID'),