manatee: Fetch schema from gitea

Point the schema input at its repo instead of a local path, so the
config builds from anywhere.

flake.lock

@@ -924,14 +924,18 @@
         ]
       },
       "locked": {
-        "lastModified": 1790705995,
-        "narHash": "sha256-Qe7ugdZbc/aXU900EKtuZOGgN4dyTgfriayoySQX2U8=",
-        "path": "/home/alex/code/schema",
-        "type": "path"
+        "lastModified": 1790709196,
+        "narHash": "sha256-vOECM4pgVkSv0bsbM3kXSCb53p4cxRL6HNsWvB2vSbY=",
+        "ref": "main",
+        "rev": "c3e9e54ac9b69c205d3582e621fffef3dd0decea",
+        "revCount": 5,
+        "type": "git",
+        "url": "ssh://gitea@git.ppp.pm:1122/alex/schema.git"
       },
       "original": {
-        "path": "/home/alex/code/schema",
-        "type": "path"
+        "ref": "main",
+        "type": "git",
+        "url": "ssh://gitea@git.ppp.pm:1122/alex/schema.git"
       }
     },
     "solo-referee": {