refactor(structure): promote app to repo root + remove redundant workspace cruft

Standard production layout: the OKR app (was nested under AINative_OKR_CASAN5/) is now
the repository root. No more wrapper directory.

- Promote AINative_OKR_CASAN5/* -> repo root (backend/ frontend/ packages/ apps/
  .specify/ docs/ infra/ nginx/ scripts/ + configs). Merge tool dirs: .gitea (kept the
  active deploy ci.yml, added harness-ci.yml + runbooks), .claude (agents/commands +
  launch.json), .github moved up.
- Remove redundant: 00_SUBMISSION_PACKAGE, scattered root notes (FPT_CASAN_Full.md,
  tu-tuong-casan.md, casan-tu-sinh..., casan_harness_assessment.md, source-review...,
  README_CASAN5_REFINED.md), casan-next-plans/ and optimize-docs/ (competition/planning
  artifacts — roadmap + design history preserved in git log / commit messages).
- Update all references to the old layout:
  - .gitea/workflows/{ci,harness-ci}.yml, .github/workflows/{ci,deploy}.yml:
    working-directory .; drop AINative_OKR_CASAN5/ prefix; .specify/{tests,scripts}
    -> packages/casan-harness/... (.specify/logs state kept)
  - .claude/launch.json, .gitea/*-runbook.md: path prefixes
  - CLAUDE.md, README.md: docs/input -> apps/okr/domain/input
  - policy-bundle.yaml: 8 policy paths -> packages/casan-harness/...; manifest re-signed
- secrets-scan.sh: fixture excludes -> new package/domain paths.

Full gate from the new root: PASS=64 FAIL=0 SKIP=3.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Dockerfile.frontend

@@ -0,0 +1,28 @@
+# ─── Stage 1: Build ──────────────────────────────────────────────────────────
+FROM node:20-alpine AS builder
+
+WORKDIR /app
+
+# VITE_API_BASE_URL is baked into the bundle at build time.
+# Use a relative path so the image works with any hostname/IP — nginx
+# running on the same host proxies /api/v1/* to the backend container.
+ARG VITE_API_BASE_URL=/api/v1
+ENV VITE_API_BASE_URL=$VITE_API_BASE_URL
+
+COPY package.json package-lock.json ./
+COPY frontend/package.json ./frontend/
+COPY backend/package.json ./backend/
+
+RUN npm ci -w frontend
+
+COPY frontend ./frontend
+
+RUN npm run build -w frontend
+
+# ─── Stage 2: nginx runtime ──────────────────────────────────────────────────
+FROM nginx:alpine AS runtime
+
+COPY --from=builder /app/frontend/dist /usr/share/nginx/html
+COPY nginx/nginx.conf /etc/nginx/conf.d/default.conf
+
+EXPOSE 80