Tech debt cleanup: fix session.py, remove stale references, update docs

- db/session.py: fix indentation (2→4 space), pool_size=0 (unlimited),
  remove "ned to look at this" typo
- Remove glue.models from alembic env.py import list
- Update shared __init__.py, menu_item.py docstring, calendar_impl.py,
  handlers/__init__.py to remove glue terminology
- Remove federation_handlers.py tombstone file
- Remove TODO comments (replace with explanatory comments)
- Rewrite README.md to reflect current architecture
- Update anchoring.py TODO to plain comment

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

db/session.py

@@ -15,7 +15,7 @@ _engine = create_async_engine(
     future=True,
     echo=False,
     pool_pre_ping=True,
-    pool_size=-1  # ned to look at this!!!
+    pool_size=0,  # 0 = unlimited (NullPool equivalent for asyncpg)
 )
 
 _Session = async_sessionmaker(
@@ -34,43 +34,42 @@ async def get_session():
         await sess.close()
 
 
-
 def register_db(app: Quart):
 
-  @app.before_request
-  async def open_session():
-      g.s = _Session()
-      g.tx = await g.s.begin()
-      g.had_error = False
+    @app.before_request
+    async def open_session():
+        g.s = _Session()
+        g.tx = await g.s.begin()
+        g.had_error = False
 
-  @app.after_request
-  async def maybe_commit(response):
-      # Runs BEFORE bytes are sent.
-      if not g.had_error and 200 <= response.status_code < 400:
-          try:
-              if hasattr(g, "tx"):
-                  await g.tx.commit()
-          except Exception as e:
-              print(f'commit failed {e}')
-              if hasattr(g, "tx"):
-                  await g.tx.rollback()
-              from quart import make_response
-              return await make_response("Commit failed", 500)
-      return response
+    @app.after_request
+    async def maybe_commit(response):
+        # Runs BEFORE bytes are sent.
+        if not g.had_error and 200 <= response.status_code < 400:
+            try:
+                if hasattr(g, "tx"):
+                    await g.tx.commit()
+            except Exception as e:
+                print(f'commit failed {e}')
+                if hasattr(g, "tx"):
+                    await g.tx.rollback()
+                from quart import make_response
+                return await make_response("Commit failed", 500)
+        return response
 
-  @app.teardown_request
-  async def finish(exc):
-      try:
-          # If an exception occurred OR we didn't commit (still in txn), roll back.
-          if hasattr(g, "s"):
-              if exc is not None or g.s.in_transaction():
-                  if hasattr(g, "tx"):
-                      await g.tx.rollback()
-      finally:
-          if hasattr(g, "s"):
-              await g.s.close()
+    @app.teardown_request
+    async def finish(exc):
+        try:
+            # If an exception occurred OR we didn't commit (still in txn), roll back.
+            if hasattr(g, "s"):
+                if exc is not None or g.s.in_transaction():
+                    if hasattr(g, "tx"):
+                        await g.tx.rollback()
+        finally:
+            if hasattr(g, "s"):
+                await g.s.close()
 
-  @app.errorhandler(Exception)
-  async def mark_error(e):
-      g.had_error = True
-      raise
+    @app.errorhandler(Exception)
+    async def mark_error(e):
+        g.had_error = True
+        raise