feat: add Docker deployment and Gitea Actions CI/CD

Add multi-stage Dockerfile, docker-compose with persistent volumes,
and Gitea Actions workflows for CI (lint/test/build) and releases
(tag, Docker image push, changelog). Support DATABASE_PATH env var
for configurable SQLite location to enable proper volume mounting.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -0,0 +1,17 @@
+services:
+  gearbox:
+    build: .
+    container_name: gearbox
+    ports:
+      - "3000:3000"
+    environment:
+      - NODE_ENV=production
+      - DATABASE_PATH=./data/gearbox.db
+    volumes:
+      - gearbox-data:/app/data
+      - gearbox-uploads:/app/uploads
+    restart: unless-stopped
+
+volumes:
+  gearbox-data:
+  gearbox-uploads: