Add quarter-based ETA setting for feedback items

Description: Enable setting ETAs on feedback items using quarter-based values (e.g., Q1 2026) in addition to specific dates. Provide a simple UI control to choose quarter and year, display the value consistently, and support filtering/sorting by quarter. Problem: Teams often plan by quarters rather than exact dates. Requiring a specific date (or having no structured ETA) leads to inaccurate timelines, inconsistent reporting, and manual workarounds (labels/notes). This makes prioritization and communication harder and causes churn when dates shift within a quarter. Benefit: Quarter-based ETAs align with common planning cadences, improve data consistency, and make roadmaps and reports clearer. They reduce noise from frequent date changes, support better filtering and prioritization, and set realistic expectations for stakeholders.