Issue list rows redesign (Linear-dense 36px): status/priority icons, votes, avatars, dates, hover affordances, no "Move" pill

Part of PAR-357. Depends on the status/priority icon and density tasks.

Problem (issues list, project issues, release issues)

• Rows are sparse. Each row is ID + title + "· High" text + grey label pills + a letter-circle and username on the far right. There is a large dead gap between the title and the labels.
• No status icon in the row, so the status shows only through the group header.
• Avatars are letter circles with the username as text, and assignee is blank when unassigned (no ghost avatar).
• No due date or updated date by default.
• No row hover state, and no "+" in group headers to add an issue to that status.
• Editors get a "Move" pill Menu on every row (IssueListDnd.tsx:274-280), which is visual clutter.
• Release detail refs are misaligned. Ref widths aren't fixed: PAR-107 pushes its title right, compared with PAR-10.

Reference

Linear list (Mobbin, dark). Each row runs: priority icon, ID (fixed width, muted), status icon, title, then parent breadcrumb, label dots, project chip, due date, avatar and created date. Group headers are a sticky band with icon, name, count and a "+" on the right.

Do

• Lay out the row as above.
• Give the ID column a fixed width and tabular numerals.
• Add hover and selected backgrounds, and make group headers sticky with "+" quick-add.
• Make every property cell a click target that opens its picker inline for signed-in editors, which removes the need for "Move".
• Use a ghost avatar for unassigned issues and a tooltip with the full name.