feat: initialize blog app with blueprints and templates

Extract blog-specific code from the coop monolith into a standalone
repository. Includes auth, blog, post, admin, menu_items, snippets
blueprints, associated templates, Dockerfile (APP_MODULE=app:app),
entrypoint, and Gitea CI workflow.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

bp/post/services/post_data.py

@@ -0,0 +1,42 @@
+from ...blog.ghost_db import DBClient  # adjust import path
+from sqlalchemy import select
+from models.ghost_content import PostLike
+from quart import g
+
+async def post_data(slug, session, include_drafts=False):
+  client = DBClient(session)
+  posts = (await client.posts_by_slug(slug, include_drafts=include_drafts))
+
+  if not posts:
+      # 404 page (you can make a template for this if you want)
+      return None
+  post, original_post = posts[0]
+
+  # Check if current user has liked this post
+  is_liked = False
+  if g.user:
+      liked_record = await session.scalar(
+          select(PostLike).where(
+              PostLike.user_id == g.user.id,
+              PostLike.post_id == post["id"],
+              PostLike.deleted_at.is_(None),
+          )
+      )
+      is_liked = liked_record is not None
+
+  # Add is_liked to post dict
+  post["is_liked"] = is_liked
+
+  tags=await client.list_tags(
+    limit=50000
+  )  # <-- new
+  authors=await client.list_authors(
+    limit=50000
+  )
+
+  return {
+      "post": post,
+      "original_post": original_post,
+      "tags": tags,
+      "authors": authors,
+  }