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_operations.py

@@ -0,0 +1,58 @@
+from __future__ import annotations
+
+from typing import Optional
+
+from sqlalchemy import select, func, update
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from models.ghost_content import Post, PostLike
+
+
+async def toggle_post_like(
+    session: AsyncSession,
+    user_id: int,
+    post_id: int,
+) -> tuple[bool, Optional[str]]:
+    """
+    Toggle a post like for a given user using soft deletes.
+    Returns (liked_state, error_message).
+    - If error_message is not None, an error occurred.
+    - liked_state indicates whether post is now liked (True) or unliked (False).
+    """
+
+    # Verify post exists
+    post_exists = await session.scalar(
+        select(Post.id).where(Post.id == post_id, Post.deleted_at.is_(None))
+    )
+    if not post_exists:
+        return False, "Post not found"
+
+    # Check if like exists (not deleted)
+    existing = await session.scalar(
+        select(PostLike).where(
+            PostLike.user_id == user_id,
+            PostLike.post_id == post_id,
+            PostLike.deleted_at.is_(None),
+        )
+    )
+
+    if existing:
+        # Unlike: soft delete the like
+        await session.execute(
+            update(PostLike)
+            .where(
+                PostLike.user_id == user_id,
+                PostLike.post_id == post_id,
+                PostLike.deleted_at.is_(None),
+            )
+            .values(deleted_at=func.now())
+        )
+        return False, None
+    else:
+        # Like: add a new like
+        new_like = PostLike(
+            user_id=user_id,
+            post_id=post_id,
+        )
+        session.add(new_like)
+        return True, None