chore(eslint): enable no-restricted-imports; replace moment with luxon (#2422)

Removes the `no-restricted-imports: off` override so the obsidianmd recommended
rule applies (bans axios/node-fetch/moment/etc.). Replaces the two `moment(...)`
call sites in `src/utils.ts` with `luxon`'s `DateTime` (already a dep) and adds
unit tests covering local/UTC formatting, zero-padding, immutability, and the
invalid-input fallback. Integration tests get a per-file override since they
need `node-fetch` to polyfill jsdom fetch. `no-restricted-globals` stays
disabled — banning the global `app` will land in a separate PR.

eslint.config.mjs

@@ -109,7 +109,6 @@ export default [
       "@typescript-eslint/no-deprecated": "off",
 
       // SDL / import / no-unsanitized / depend: defer — review separately
-      "no-restricted-imports": "off",
       "no-restricted-globals": "off",
     },
   },
@@ -128,6 +127,15 @@ export default [
     },
   },
 
+  // Integration tests bootstrap jsdom fetch via `node-fetch` polyfill —
+  // allow the otherwise-banned import here only.
+  {
+    files: ["src/integration_tests/**"],
+    rules: {
+      "no-restricted-imports": "off",
+    },
+  },
+
   // Node-context files (build configs, scripts)
   {
     files: [