chore: checkpoint ai search comments and i18n foundation

backend/migration/src/m20260328_000007_create_ai_chunks.rs

@@ -0,0 +1,33 @@
+use loco_rs::schema::*;
+use sea_orm_migration::prelude::*;
+
+#[derive(DeriveMigrationName)]
+pub struct Migration;
+
+#[async_trait::async_trait]
+impl MigrationTrait for Migration {
+    async fn up(&self, manager: &SchemaManager) -> Result<(), DbErr> {
+        create_table(
+            manager,
+            "ai_chunks",
+            &[
+                ("id", ColType::PkAuto),
+                ("source_slug", ColType::String),
+                ("source_title", ColType::StringNull),
+                ("source_path", ColType::StringNull),
+                ("source_type", ColType::String),
+                ("chunk_index", ColType::Integer),
+                ("content", ColType::Text),
+                ("content_preview", ColType::StringNull),
+                ("embedding", ColType::JsonBinaryNull),
+                ("word_count", ColType::IntegerNull),
+            ],
+            &[],
+        )
+        .await
+    }
+
+    async fn down(&self, manager: &SchemaManager) -> Result<(), DbErr> {
+        drop_table(manager, "ai_chunks").await
+    }
+}