fix: deploy crash from MutableHeaders.pop + missing wget

Two issues blocked the security-fix deploy:

1. Starlette's MutableHeaders has no .pop() — del-via-membership is the
   correct mapping op. The previous code crashed every request with
   AttributeError, taking the container's healthcheck down with it.

2. Coolify's in-container healthcheck falls back to wget which wasn't
   installed in our slim base. Add wget alongside curl.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -22,9 +22,9 @@ ENV PYTHONUNBUFFERED=1 \
 WORKDIR /app
 
 # gcc — for any pure-Python wheels without prebuilt slim wheels.
-# curl  — Coolify runs its healthcheck via curl inside the container.
+# curl + wget — Coolify falls back to wget for its in-container healthcheck.
 RUN apt-get update \
-    && apt-get install -y --no-install-recommends gcc curl \
+    && apt-get install -y --no-install-recommends gcc curl wget \
     && rm -rf /var/lib/apt/lists/*
 
 # Install Python deps from pyproject.