Feat: add storage interface; add sqlite impl

storage/migrations/001_init.up.sql

@@ -0,0 +1,7 @@
+CREATE TABLE chat (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    name TEXT NOT NULL,
+    msgs TEXT NOT NULL,  -- Store messages as a comma-separated string
+    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
+);