fix: correct Dockerfile path in Fly.io deployment

The deployment was failing because flyctl was looking for the Dockerfile
at demo/demo/Dockerfile instead of demo/Dockerfile. When --config points
to demo/fly.toml, flyctl changes context to the demo/ directory, so the
dockerfile path should be relative to that location.

Changes:
- Updated fly.toml to use relative path "Dockerfile" instead of "demo/Dockerfile"
- Removed redundant --dockerfile flag from workflow (path already in fly.toml)

Author: ukutaht

.github/workflows/fly-deploy.yml

@@ -14,6 +14,6 @@ jobs:
       - uses: actions/checkout@v4
       - uses: superfly/flyctl-actions/setup-flyctl@master
       - name: Deploy demo app to Fly.io
-        run: flyctl deploy --remote-only --config demo/fly.toml --dockerfile demo/Dockerfile --build-arg BUILD_CONTEXT=.
+        run: flyctl deploy --remote-only --config demo/fly.toml --build-arg BUILD_CONTEXT=.
         env:
           FLY_API_TOKEN: ${{ secrets.FLY_API_TOKEN }}

demo/fly.toml

@@ -8,7 +8,7 @@ primary_region = 'arn'
 kill_signal = 'SIGTERM'
 
 [build]
-  dockerfile = "demo/Dockerfile"
+  dockerfile = "Dockerfile"
 
 [env]
   PHX_HOST = 'prima-lingering-feather-539.fly.dev'