feat: add semantic-release for automated versioning and help dialog

- Set up semantic-release with zero-touch CI pipeline on push to main
- Add version sync script to keep all package.json files and APP_VERSION
  constant in sync automatically
- Consolidate Docker publishing into single tag-triggered workflow that
  pushes to both Docker Hub and ghcr.io with semver tags
- Add help dialog with keyboard shortcuts, getting started guide, and
  resource links
- Sync all versions to 0.2.1 to match Docker Hub latest

.releaserc.json

@@ -0,0 +1,44 @@
+{
+  "branches": ["main"],
+  "plugins": [
+    "@semantic-release/commit-analyzer",
+    "@semantic-release/release-notes-generator",
+    [
+      "@semantic-release/changelog",
+      {
+        "changelogFile": "CHANGELOG.md"
+      }
+    ],
+    [
+      "@semantic-release/npm",
+      {
+        "npmPublish": false
+      }
+    ],
+    [
+      "@semantic-release/exec",
+      {
+        "prepareCmd": "./scripts/sync-version.sh ${nextRelease.version}"
+      }
+    ],
+    [
+      "@semantic-release/git",
+      {
+        "assets": [
+          "package.json",
+          "pnpm-lock.yaml",
+          "CHANGELOG.md",
+          "apps/web/package.json",
+          "apps/api/package.json",
+          "apps/docs/package.json",
+          "packages/shared/package.json",
+          "packages/shared/src/constants.ts",
+          "packages/image-engine/package.json",
+          "packages/ai/package.json"
+        ],
+        "message": "chore(release): ${nextRelease.version} [skip ci]\n\n${nextRelease.notes}"
+      }
+    ],
+    "@semantic-release/github"
+  ]
+}