chore: bootstrap repo scaffolding (M0.1)

Adds the §1.2 scaffolding required by IMPLEMENTATION_PLAN.md M0.1:
README, CONTRIBUTING, CODEOWNERS, CHANGELOG, PR + issue templates,
CI workflow, release workflow, LICENSE, commitlint, cliff config,
.editorconfig, .gitignore, .env.example.

Refs: M0.1

.gitea/workflows/ci.yaml

@@ -0,0 +1,35 @@
+# CI for orca-platform (IaC). Runs `orca validate` only.
+name: ci
+
+on:
+  pull_request:
+    branches: [main]
+  push:
+    branches: [main]
+
+jobs:
+  shared:
+    runs-on: docker
+    steps:
+      - uses: actions/checkout@v4
+        with: { fetch-depth: 0 }
+
+      - name: commitlint (PR only)
+        if: github.event_name == 'pull_request'
+        uses: wagoid/commitlint-github-action@v6
+
+      - name: gitleaks
+        uses: gitleaks/gitleaks-action@v2
+
+  validate:
+    runs-on: docker
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: install orca
+        run: |
+          curl -fsSL https://orca.meghsakha.com/install.sh | sh
+          orca version
+
+      - name: orca validate
+        run: orca validate ./