feat: add Gitea CI workflow with podman-based lint and link check

- Markdown lint via markdownlint-cli2 container
- Internal cross-reference checker for See Also sections
- Both jobs run on linux runner using podman containers

.markdownlint-cli2.yaml

@@ -0,0 +1,29 @@
+config:
+  # Allow long lines in tables and code blocks
+  MD013:
+    line_length: 200
+    tables: false
+    code_blocks: false
+
+  # Allow duplicate headings across files (common in howtos)
+  MD024:
+    siblings_only: true
+
+  # Allow trailing punctuation in headings (e.g. "~/.ssh/config")
+  MD026: false
+
+  # Allow inline HTML (rare but sometimes needed)
+  MD033: false
+
+  # Allow bare URLs in markdown
+  MD034: false
+
+  # Allow multiple blank lines
+  MD012: false
+
+globs:
+  - "**/*.md"
+
+ignores:
+  - ".git"
+  - ".venv"