chore(infra): wire MLflow/Airflow env vars, fix healthcheck, add .dockerignore

- docker-compose: pass ML_SERVING_URL, MLFLOW_URL, AIRFLOW_URL + creds to api service
- docker-compose: pass NEXT_PUBLIC_MLFLOW_URL/AIRFLOW_URL to admin service
- docker-compose: replace wget healthcheck with node fetch (wget not in node image)
- docker-compose: enable Airflow basic_auth API backend; add MLflow pip dep for DAGs
- Dockerfiles: tighten layer caching, add .dockerignore

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

infra/docker/Dockerfile.admin

@@ -1,21 +1,22 @@
-FROM node:22-alpine AS base
-RUN npm install -g pnpm
+# syntax=docker/dockerfile:1.7
 
-FROM base AS deps
-WORKDIR /app
-COPY package.json pnpm-workspace.yaml pnpm-lock.yaml* ./
-COPY packages/shared-types/package.json ./packages/shared-types/
-COPY apps/admin/package.json ./apps/admin/
-RUN pnpm install --frozen-lockfile
+FROM node:22-slim AS base
+RUN apt-get update && apt-get install -y --no-install-recommends ca-certificates \
+ && rm -rf /var/lib/apt/lists/* \
+ && npm install -g pnpm
+ENV CI=true \
+    PNPM_HOME=/pnpm \
+    PATH=/pnpm:$PATH
+RUN pnpm config set store-dir /pnpm/store
 
 FROM base AS builder
 WORKDIR /app
-COPY --from=deps /app/node_modules ./node_modules
-COPY --from=deps /app/packages/shared-types/node_modules ./packages/shared-types/node_modules
-COPY --from=deps /app/apps/admin/node_modules ./apps/admin/node_modules
-COPY tsconfig.base.json ./
-COPY packages/shared-types ./packages/shared-types
-COPY apps/admin ./apps/admin
+COPY pnpm-lock.yaml ./
+RUN --mount=type=cache,id=pnpm,target=/pnpm/store pnpm fetch
+COPY . .
+RUN --mount=type=cache,id=pnpm,target=/pnpm/store \
+    pnpm install --frozen-lockfile --offline \
+      --filter @oo/admin... --filter @oo/shared-types
 RUN pnpm --filter @oo/shared-types build
 ARG NEXT_PUBLIC_MLFLOW_URL=/mlflow
 ARG NEXT_PUBLIC_AIRFLOW_URL=/airflow
@@ -24,7 +25,7 @@ ENV NEXT_TELEMETRY_DISABLED=1 \
     NEXT_PUBLIC_AIRFLOW_URL=$NEXT_PUBLIC_AIRFLOW_URL
 RUN pnpm --filter @oo/admin build
 
-FROM node:22-alpine AS runner
+FROM node:22-slim AS runner
 ENV NODE_ENV=production NEXT_TELEMETRY_DISABLED=1 PORT=3080
 WORKDIR /app
 COPY --from=builder /app/apps/admin/.next/standalone ./