feat(cms): U1 content model + migration scaffold for blog/news/events

Establish content/ as the source of truth for editable content and
back-fill it from the existing detail pages, per U1 of the no-code CMS
plan.

- docs/content-model.md: front-matter schema (EN/MK/SI), body_format
  html-vs-markdown, content/events -> projects/ output mapping.
- tools/migrate_pages_to_content.py: bs4/yaml extractor; pulls title,
  subtitle, category, ISO date (from ARTICLE_DATES), hero image+caption;
  preserves the article body PLUS trailing sibling sections (event
  galleries) verbatim as body_format: html. Reports unparseable pages
  instead of emitting half-formed files.
- content/**: 51 files (17 entries x EN/MK/SI), 0 skips.
- tools/tests/test_migrate_roundtrip.py: 12 characterization tests
  (structured fields, news-has-no-subtitle, event gallery/lightbox
  preserved, Cyrillic UTF-8 round-trip, every page parses).
- .gitignore: ignore __pycache__/ and *.pyc.

U1 is unblocked and standalone. U2 (render content -> pages) is next;
U5/U6 remain blocked on Open Question Q1 (Gitea<->GitHub topology).

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

.gitignore

@@ -3,3 +3,5 @@ images/original/
 .playwright-mcp/
 code_export.txt
 images/_originals/
+__pycache__/
+*.pyc