fix: Stack title overflows into cards for read-only board members

Bug description

For users with read-only access to a board (canManage = false) or on archived boards, the list/stack column header title wraps to multiple lines and visually overlaps the cards below it. Users with manage rights see the title correctly truncated with ….

Steps to reproduce

1. Share a board with a user as read-only (no manage rights)
2. Log in as that user and open the board
3. The board must have at least one list with a long title

Result: Title wraps to multiple lines and overlaps the cards.
Expected: Title is truncated to a single line with …

Root cause

In src/components/board/Stack.vue there are two <h3> branches:

• Manageable (v-else-if="!editing"): has class="stack__title" → gets white-space: nowrap; overflow: hidden; text-overflow: ellipsis → correct.
• Read-only / archived (v-if="!canManage || isArchived"): plain <h3> without the class → no overflow constraints → wraps freely.

Environment

• Affects all browsers (Chrome, Firefox, WebKit)
• Reproducible on Nextcloud Deck v1.17.1

Start in src/components/board/Stack.vue and compare the two h3 branches for manageable and read-only or archived boards, checking how the title styles differ. Reproduce with a long list title on a read-only or archived board, then verify the title stays on one line with an ellipsis without overlapping the cards.