ci: eliminate cold pnpm install via pre-baked CI base image (Phase 1)

Every pipeline ran a cold pnpm install (network fetch + musl native
rebuilds + apk add python3 make g++), median ~731s, paid twice per push.

Phase 1 (no cluster access, repo commits only):
- Dockerfile.ci: node:22-alpine + python3/make/g++/postgresql-client +
  pnpm@10.6.2 + pnpm fetch to warm the store and compile natives once.
- .woodpecker/ci-image.yml: kaniko build/push of ci-base:latest + a
  lockfile-hash tag, triggered only when pnpm-lock.yaml or Dockerfile.ci
  change. Reuses the publish.yml kaniko/auth pattern.
- ci.yml + publish.yml: install from the baked ci-base:latest, drop the
  per-run apk add, use pnpm install --frozen-lockfile --prefer-offline.
- Framework monorepo template: single cached install other steps depend
  on instead of re-running npm ci across 6 steps.

Node 22->24 bump is a separate follow-up PR. Phase 2 (RWX Longhorn PVC)
is out of scope. Expected install ~731s -> ~30-60s.

Refs #634

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.woodpecker/publish.yml

@@ -2,7 +2,9 @@
 # Runs only on main branch push/tag
 
 variables:
-  - &node_image 'node:22-alpine'
+  # Pre-baked CI base (see .woodpecker/ci-image.yml): node:22-alpine +
+  # toolchain + warm pnpm store. Kills the second cold install publish pays.
+  - &node_image 'git.mosaicstack.dev/mosaicstack/stack/ci-base:latest'
   - &enable_pnpm 'corepack enable'
   # Heavy kaniko image builds (~25 min) — gate them so a merge that only touches
   # the npm-only CLI (@mosaicstack/mosaic) or docs does NOT rebuild the platform
@@ -31,7 +33,8 @@ steps:
     image: *node_image
     commands:
       - corepack enable
-      - pnpm install --frozen-lockfile
+      # Resolve from the baked pnpm store instead of a cold network fetch.
+      - pnpm install --frozen-lockfile --prefer-offline
 
   build:
     image: *node_image