Reapply "models: remove legacy template-function-faker plugin row"

This reverts commit 773c4a24a5.

crates/yaak-models/build.rs

@@ -0,0 +1,5 @@
+fn main() {
+    // Migrations are embedded with include_dir!, so trigger rebuilds when SQL files change.
+    println!("cargo:rerun-if-changed=migrations");
+    println!("cargo:rerun-if-changed=blob_migrations");
+}

crates/yaak-models/migrations/20260217000000_remove-legacy-faker-plugin.sql

@@ -0,0 +1,3 @@
+-- Remove stale plugin rows left over from the brief period when faker shipped as bundled.
+DELETE FROM plugins
+WHERE directory LIKE '%template-function-faker';