Add initial linting and security checks

Introduces CI workflows for YAML linting and secret detection,
and adds basic configuration for both tools. Also adds a
sample connectivity test playbook.

.gitea/workflows/yamllint_and_pass_check.yml

@@ -0,0 +1,23 @@
+---
+name: YAML Lint
+
+on: [push]
+
+jobs:
+  yamllint:
+    runs-on: ubuntu-yamllint
+    steps:
+      - name: Checkout linting
+        uses: actions/checkout@v4
+      - name: Run yamllint with auto-detected config
+        run: yamllint -c .yamllint .
+  gitleaks:
+    runs-on: ubuntu-yamllint
+    steps:
+      - name: Checkout passwords leaks
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - name: Run gitleaks
+        run: gitleaks detect --source .
+...