chore: initialize repository with project rules, docs, and phase-1 ADRs

Set up the foundation for the adastra-portal project:

- CLAUDE.md captures durable project rules (quality bar, security/perf/a11y
  as first-class, language, commit conventions, ADR proactivity).
- docs/ and decisions/ scaffolding with maintained indexes (docs/README.md
  and decisions/README.md), MADR 4.0.0 template, and tag vocabulary.
- Phase-1 ADRs (0001-0006) lock structural choices: ADR usage, Nx monorepo
  with the apps preset, naming convention (adastra-portal / portal-shell /
  portal-bff), Angular CSR/zoneless/Signals/Vitest, NestJS over Express,
  PostgreSQL with Prisma.
- docs/setup/ guides translated to English.
- .gitignore covers Node/Nx artifacts and the personal notes/ scratchpad.

The Nx workspace itself is not yet bootstrapped; that step is gated on a
revised setup guide aligned with the ADRs.

.gitignore

@@ -0,0 +1,45 @@
+# Dependencies
+node_modules/
+.pnpm-store/
+
+# Build outputs
+dist/
+build/
+out-tsc/
+tmp/
+.nx/cache/
+.nx/workspace-data/
+
+# Test artifacts
+coverage/
+.test-output/
+
+# Logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+pnpm-debug.log*
+
+# Environment / secrets
+.env
+.env.local
+.env.*.local
+*.pem
+*.key
+
+# OS / editor scrap
+.DS_Store
+Thumbs.db
+*.swp
+*~
+.idea/
+
+# VS Code: keep shared settings, ignore local overrides
+.vscode/*.local
+.vscode/*.code-workspace
+
+# Claude Code: keep shared settings, ignore local overrides
+.claude/settings.local.json
+
+# Personal scratchpad — see CLAUDE.md
+notes/