web-app-minio: enable OIDC integration and policy handling

- Added OIDC and LDAP feature flags in config
- Introduced API/Console URL vars for proxy alignment
- Implemented automatic MinIO policy creation for OIDC admin group
- Replaced static env.J2 with dynamic env.j2 (OIDC-aware)
- Added policy.json.j2 template with full admin rights
- Cleaned up tasks to use stdin instead of file for mc policy apply

Ref: https://chatgpt.com/share/68d1d3ef-ca84-800f-abe2-11ab70e20c4e

roles/web-app-minio/templates/policy.json.j2

@@ -0,0 +1,16 @@
+{
+  "Version": "2012-10-17",
+  "Statement": [
+    {
+      "Effect": "Allow",
+      "Action": [
+        "s3:*",
+        "admin:*"
+      ],
+      "Resource": [
+        "arn:aws:s3:::*",
+        "arn:minio:admin:::*"
+      ]
+    }
+  ]
+}