manatee: Add schema

The household weekly plan at schema.ppp.pm: its module, certificate,
DNS record, backup and secrets. The link to puppy-tracker is prepared
but commented out until puppy-tracker with the integration feed is
deployed.

flake.lock

@@ -910,12 +910,30 @@
         "nixpkgs": "nixpkgs_3",
         "pppdotpm-site": "pppdotpm-site",
         "puppy-tracker": "puppy-tracker",
+        "schema": "schema",
         "solo-referee": "solo-referee",
         "todo": "todo",
         "whib-backend": "whib-backend",
         "whib-frontend": "whib-frontend"
       }
     },
+    "schema": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1790705995,
+        "narHash": "sha256-Qe7ugdZbc/aXU900EKtuZOGgN4dyTgfriayoySQX2U8=",
+        "path": "/home/alex/code/schema",
+        "type": "path"
+      },
+      "original": {
+        "path": "/home/alex/code/schema",
+        "type": "path"
+      }
+    },
     "solo-referee": {
       "inputs": {
         "flake-utils": "flake-utils_4",