feat(deploy): pre-start drizzle-kit migrate init container

One-shot migrate container runs drizzle-kit migrate against DATABASE_URL
and exits 0 before web boots. web service depends_on with condition
service_completed_successfully, so failed migrations block web startup
instead of serving 500s against a stale schema. Broker deliberately does
NOT depend on migrate - it tolerates DB-down gracefully per DEPLOY_SPEC
and should keep serving WS peers even during migration failures.

Also excludes apps/cli from docker build context (CLI ships to npm, not
containers) to sidestep zod spec drift in its package.json vs lockfile.

Known followup: migrate image is 3.27GB due to pnpm catalog: specifiers
forcing full-workspace resolution. pnpm deploy bundle trim is a P2.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/db/Dockerfile

@@ -0,0 +1,42 @@
+# claudemesh db — drizzle-kit migration runner
+# One-shot container: runs `drizzle-kit migrate` against $DATABASE_URL then exits 0.
+# Used as a pre-deploy init container so the web service never starts against a
+# schema it doesn't know about.
+#
+# Build from repo root:  docker build -f packages/db/Dockerfile -t claudemesh-migrate .
+
+# Stage 1: resolve pnpm workspace + install deps (Bun base + standalone pnpm)
+FROM oven/bun:1.2 AS deps
+WORKDIR /app
+
+RUN apt-get update && apt-get install -y --no-install-recommends curl ca-certificates && \
+    curl -fsSL "https://github.com/pnpm/pnpm/releases/download/v10.25.0/pnpm-linuxstatic-x64" -o /usr/local/bin/pnpm && \
+    chmod +x /usr/local/bin/pnpm && \
+    rm -rf /var/lib/apt/lists/*
+
+# pnpm needs full workspace context to resolve workspace:* and catalog: specifiers
+COPY . .
+
+# drizzle-kit is a devDependency → install the full dep graph (NOT --prod).
+# Filter to db + its transitive deps only → ~20x smaller install than the whole workspace.
+RUN pnpm install --frozen-lockfile --ignore-scripts --filter "@turbostarter/db..."
+
+# Stage 2: minimal Bun runtime (executes drizzle-kit CLI + TS config)
+FROM oven/bun:1.2-slim AS runtime
+WORKDIR /app
+
+ENV NODE_ENV=production
+
+# Copy workspace metadata, the db package (schema + migrations + config), shared (transitive)
+COPY --from=deps --chown=bun:bun /app/package.json /app/pnpm-workspace.yaml /app/pnpm-lock.yaml /app/.npmrc ./
+COPY --from=deps --chown=bun:bun /app/node_modules ./node_modules
+COPY --from=deps --chown=bun:bun /app/packages/db ./packages/db
+COPY --from=deps --chown=bun:bun /app/packages/shared ./packages/shared
+COPY --from=deps --chown=bun:bun /app/tooling/typescript ./tooling/typescript
+
+USER bun
+WORKDIR /app/packages/db
+
+# drizzle-kit reads DATABASE_URL from env via ./src/env.ts, runs pending migrations,
+# exits 0 on success / non-zero on failure. No long-running process.
+CMD ["bun", "x", "drizzle-kit", "migrate"]