feat(db): non-empty CHECK constraints on object text columns

crates/db/migrations/0003_object.sql

@@ -1,16 +1,17 @@
 -- Catalogue objects (the inventory-minimum core). One row = one object or a group.
 CREATE TABLE object (
     id                UUID PRIMARY KEY,
-    object_number     TEXT NOT NULL UNIQUE,
-    object_name       TEXT NOT NULL,
+    object_number     TEXT NOT NULL UNIQUE CHECK (object_number <> ''),
+    object_name       TEXT NOT NULL CHECK (object_name <> ''),
     number_of_objects INTEGER NOT NULL DEFAULT 1 CHECK (number_of_objects >= 1),
-    brief_description TEXT,
-    current_location  TEXT,
-    current_owner     TEXT,
-    recorder          TEXT,
+    brief_description TEXT CHECK (brief_description <> ''),
+    current_location  TEXT CHECK (current_location <> ''),
+    current_owner     TEXT CHECK (current_owner <> ''),
+    recorder          TEXT CHECK (recorder <> ''),
     recording_date    DATE,
     visibility        TEXT NOT NULL DEFAULT 'draft'
                           CHECK (visibility IN ('draft', 'internal', 'public')),
+    -- updated_at is maintained by the repository (set to now() on update).
     created_at        TIMESTAMPTZ NOT NULL DEFAULT now(),
     updated_at        TIMESTAMPTZ NOT NULL DEFAULT now()
 );