fix(docker): pin api image to uv.lock to escape greenlet 3.5.0

Cloud Build trigger 1e9fc847 (build a12d85eb) failed with:

    hint: You're on Linux (manylinux_2_41_x86_64), but greenlet (v3.5.0)
    only has wheels for the following platforms: macosx_11_0_universal2,
    win_arm64
    error: Distribution greenlet==3.5.0 ... can't be installed because
    it doesn't have a source distribution or wheel for the current
    platform

The Dockerfile copied `pyproject.toml` but not `uv.lock`, and ran
`uv sync` (re-resolves from pyproject) instead of `uv sync --frozen`
(honors uv.lock). uv.lock pins greenlet 3.2.4 which has full
linux/x86_64 wheel coverage; the 3.5.0 release only shipped macOS +
win_arm64 wheels and broke any image built without the lock.

Adds `COPY uv.lock .` and switches `uv sync` → `uv sync --frozen`.

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

Author: MarkusNeusinger

api/Dockerfile

@@ -12,12 +12,15 @@ RUN apt-get update && apt-get install -y \
 
 # Copy requirements first for better caching
 COPY pyproject.toml .
+COPY uv.lock .
 COPY README.md .
 
-# Install uv and create venv
+# Install uv and create venv. `--frozen` honors uv.lock instead of re-resolving
+# from pyproject.toml — without it, uv picked up greenlet 3.5.0, which only
+# ships macOS/Windows wheels and breaks the linux/amd64 Cloud Build image.
 RUN pip install --no-cache-dir uv && \
     uv venv && \
-    uv sync
+    uv sync --frozen
 
 # Copy application code
 COPY api/ ./api/