Comment replies and comment editing restriction

This document describes two related comment features (initial MVP versions).

Threaded replies (issue #5907)

Comments on a card can now reply to a specific earlier comment.

• Each card comment has an optional parentId field referencing the _id of the comment it replies to. Top-level comments leave it empty.
• A Reply link appears next to each comment (for board members). Clicking it opens the new-comment form with an "In reply to ..." banner showing the parent comment text; the banner can be cancelled to post a normal top-level comment.
• Replies are rendered indented beneath the thread, and also show an "In reply to: <parent text>" quote for context.

MVP limitations

• Threading is a single visual level of indentation; replies-to-replies are all indented the same amount rather than nested arbitrarily deep.
• Ordering still follows comment creation time; replies are not re-grouped directly under their parent.
• Deleting a parent comment does not delete or re-parent its replies; the "In reply to" quote simply disappears if the parent is gone.

Restrict comment editing (issue #5906)

A board-level setting controls whether board admins may moderate other users' comments.

• Board setting: restrictCommentEditing (Boolean, default false).
  • false (default): historical behaviour — board admins may edit/delete any comment on the board.
  • true: board admins may not edit or delete comments authored by other users. Only the comment's own author can edit/delete it.
• Enforcement lives on the server in models/cardComments.js via before.update / before.remove collection hooks, which throw a Meteor.Error when the action is not allowed. The UI also hides the edit/delete links accordingly, using the same decision function.
• The decision is a pure, unit-tested function canEditComment({ isAuthor, isBoardAdmin, restrictCommentEditing }) exported from models/cardComments.js.

Getter / setter

Boards documents gain:

• board.getRestrictCommentEditing() — returns the boolean.
• board.setRestrictCommentEditing(value) — updates the setting.

MVP limitations

• No dedicated Admin Panel / board-settings UI toggle is wired up yet; the setting is enforced end to end but is currently set programmatically / via the API. A board-settings checkbox can be added later.