feat: project scaffold with SSH server and placeholder TUI

Sets up Go module, Wish/BubbleTea SSH server on port 2222, placeholder
TUI model showing "Welcome to Catacombs!", Dockerfile, and docker-compose.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -0,0 +1,11 @@
+services:
+  catacombs:
+    build: .
+    ports:
+      - "2222:2222"
+    volumes:
+      - catacombs-data:/app/data
+    restart: unless-stopped
+
+volumes:
+  catacombs-data: