feat: first cut at openai compatible server

migrations/20260725000000_add_endpoint_port/down.sql

@@ -0,0 +1 @@
+ALTER TABLE preferences DROP COLUMN endpoint_port;

migrations/20260725000000_add_endpoint_port/up.sql

@@ -0,0 +1,2 @@
+ALTER TABLE preferences ADD COLUMN endpoint_port INTEGER NOT NULL DEFAULT 4000
+    CHECK (endpoint_port BETWEEN 1 AND 65535);