chore(ci): add Docker BuildKit examples, .dockerignore, CI cache docs; tune vite config

documentation/AE_Docker_CI_cache_policy.md

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+# AE Docker CI Cache Policy (recommendation)
+
+Purpose
+- Provide a straightforward policy to keep build caches useful but bounded.
+
+Recommendations
+- Primary CI cache: **registry-based buildx cache** (preferred). Use a single cache ref (e.g. `ghcr.io/ORG/REPO:cache`) reused by CI builds.
+- Local dev cache: use `--cache-to type=local` for fast iteration but prune periodically.
+- Retention: keep registry cache for 30 days by default. Implement registry GC or lifecycle rule to delete older cache blobs.
+
+Rotation strategy
+- Option A (simple): CI always writes to the same cache ref `:cache`. Periodically (monthly) run a job to `docker pull` and `docker image rm` older tags if you use date-based tagging.
+- Option B (date-tag): CI writes cache to `cache-YYYYMMDD` and a small scheduled job deletes tags older than 30 days.
+
+Pruning commands (developer)
+- Remove local build cache older than 72 hours:
+  ```bash
+  docker builder prune --filter "until=72h" --force
+  ```
+- Remove all builder cache (aggressive):
+  ```bash
+  docker builder prune --all --force
+  ```
+
+CI runner requirements
+- `docker` and `docker buildx` available in runner environment.
+- Registry credentials provided via CI secrets with permission to push/pull images.
+
+Security & Secrets
+- Do not store registry credentials in repo. Use CI secret storage.