feat: convert ssh tunnels into a plugin

drizzle/sqlite/0034_curious_molecule_man.sql

@@ -0,0 +1,5 @@
+-- c2s_tunnel_presets moved to the tunnels plugin, whose first migration renames
+-- it to p_tunnels_presets. Dropping it here would lose every saved preset, so
+-- this only stops drizzle tracking it. SELECT 1 because MySQL rejects an
+-- empty query.
+SELECT 1;

drizzle/sqlite/meta/_journal.json

@@ -239,6 +239,13 @@
       "when": 1790189636471,
       "tag": "0033_careful_random",
       "breakpoints": true
+    },
+    {
+      "idx": 34,
+      "version": "6",
+      "when": 1790201004314,
+      "tag": "0034_curious_molecule_man",
+      "breakpoints": true
     }
   ]
 }