fix: Make Cargo.lock optional in Docker build

Cargo.lock may not exist before first build. Use wildcard copy
so Docker doesn't fail if lockfile is missing.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker/Dockerfile.api

@@ -7,7 +7,8 @@ RUN apk add --no-cache musl-dev pkgconfig openssl-dev openssl-libs-static
 WORKDIR /build
 
 # Cache dependencies — copy manifests first
-COPY Cargo.toml Cargo.lock ./
+COPY Cargo.toml ./
+COPY Cargo.lock* ./
 RUN mkdir src && echo "fn main() {}" > src/main.rs
 RUN cargo build --release 2>/dev/null || true