feat: move snippets backend and tables into a plugin (B2)

drizzle/sqlite/0030_quick_felicia_hardy.sql

@@ -0,0 +1,4 @@
+-- snippets, snippet_folders and snippet_access moved to the snippets plugin
+-- (p_snippets_*), adopted by rename rather than dropped. A real DROP TABLE
+-- here would run before the plugin's adoption migration and delete every row.
+SELECT 1;

drizzle/sqlite/meta/_journal.json

@@ -211,6 +211,13 @@
       "when": 1790166643921,
       "tag": "0029_numerous_aaron_stack",
       "breakpoints": true
+    },
+    {
+      "idx": 30,
+      "version": "6",
+      "when": 1790169397528,
+      "tag": "0030_quick_felicia_hardy",
+      "breakpoints": true
     }
   ]
 }