Initial commit: thbd-portal, duplicated from elmi-portal

Rebranded for Thunderbird Portal (THBD): numbering prefix EL->TH, all
"ELMI"/"ЭЛМИ" UI strings genericized, ELMI's real contract templates and
company legal/bank details removed (not applicable to this company), fresh
VAPID keypair and encryption key, fresh single-migration schema history.
Same architecture as elmi-portal: Web Push notifications, unread-chat app
badge, cookie-session auth.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Gh2UXUQUVBWroWEnn1FLFG

drizzle.config.ts

@@ -0,0 +1,13 @@
+import { defineConfig } from "drizzle-kit";
+import path from "node:path";
+
+const dataDir = process.env.DATA_DIR ?? path.join(process.cwd(), "data");
+
+export default defineConfig({
+  out: "./src/lib/db/migrations",
+  schema: "./src/lib/db/schema.ts",
+  dialect: "sqlite",
+  dbCredentials: {
+    url: path.join(dataDir, "db.sqlite"),
+  },
+});