fix(backend/build): Update stale Poetry usage in Dockerfile (#12124)

[SECRT-2006: Dev deployment failing: poetry not found in container
PATH](https://linear.app/autogpt/issue/SECRT-2006)

- Follow-up to #12090

### Changes 🏗️

- Remove now-broken Poetry path config values
- Remove usage of now-broken `poetry run` in container run command
- Add trigger on `backend/Dockerfile` changes to Frontend CI workflow

### Checklist 📋

#### For code changes:
- [x] I have clearly listed my changes in the PR description
- [x] I have made a test plan
- [x] I have tested my changes according to the test plan:
  - If it works, CI will pass

.github/workflows/platform-frontend-ci.yml

@@ -6,10 +6,12 @@ on:
     paths:
       - ".github/workflows/platform-frontend-ci.yml"
       - "autogpt_platform/frontend/**"
+      - "autogpt_platform/backend/Dockerfile"
   pull_request:
     paths:
       - ".github/workflows/platform-frontend-ci.yml"
       - "autogpt_platform/frontend/**"
+      - "autogpt_platform/backend/Dockerfile"
   merge_group:
   workflow_dispatch:
 

autogpt_platform/backend/Dockerfile

@@ -59,12 +59,7 @@ FROM debian:13-slim AS server
 
 WORKDIR /app
 
-ENV POETRY_HOME=/opt/poetry \
-    POETRY_NO_INTERACTION=1 \
-    POETRY_VIRTUALENVS_CREATE=true \
-    POETRY_VIRTUALENVS_IN_PROJECT=true \
-    DEBIAN_FRONTEND=noninteractive
-ENV PATH=/opt/poetry/bin:$PATH
+ENV DEBIAN_FRONTEND=noninteractive
 
 # Install Python, FFmpeg, ImageMagick, and CLI tools for agent use.
 # bubblewrap provides OS-level sandbox (whitelist-only FS + no network)
@@ -81,6 +76,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     bubblewrap \
     && rm -rf /var/lib/apt/lists/*
 
+# Copy poetry (build-time only, for `poetry install --only-root` to create entry points)
 COPY --from=builder /usr/local/lib/python3* /usr/local/lib/python3*
 COPY --from=builder /usr/local/bin/poetry /usr/local/bin/poetry
 # Copy Node.js installation for Prisma
@@ -104,11 +100,12 @@ COPY autogpt_platform/backend/poetry.lock autogpt_platform/backend/pyproject.tom
 # Copy backend code + docs (for Copilot docs search)
 COPY autogpt_platform/backend ./
 COPY docs /app/docs
-RUN poetry install --no-ansi --only-root
+RUN POETRY_VIRTUALENVS_CREATE=true POETRY_VIRTUALENVS_IN_PROJECT=true \
+    poetry install --no-ansi --only-root
 
 ENV PORT=8000
 
-CMD ["poetry", "run", "rest"]
+CMD ["rest"]
 
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