[Task] FEAT-USER-GROUPS-10: My Groups view — read list + self-remove

[sven1103-agent]

Parent Story

#1568

Requirement IDs

GROUP-R-05, GROUP-R-03, GROUP-R-02, GROUP-R-04

Description

Implement the "My Groups" view as a new settings-hub section (mirrors UserProfileMain/SettingsSection):

• New @Route("settings/groups") view MyGroupsMain + MyGroupsComponent with layout SettingsMainLayout.
• Add a "Groups" tab to SettingsNavigationComponent via addTab("Groups", VaadinIcon.USERS, MyGroupsMain.class).
• Read memberships via GroupInformationService.listMyGroups(currentUserId); render each group's name, description, type badge (ORG/ADHOC), and my internal role badge.
• MEMBER rows: self-remove wired to GroupService.removeMembership (auto-dissolve handled in the domain layer).
• OWNER/MANAGER rows: management actions rendered but disabled with a tooltip ("Available in an upcoming update — FEAT-USER-GROUPS-04").
• ORG rows: membership-only info, no owner-equivalent controls (structural AC 5).

Acceptance Criteria (from parent Story)

From parent Story #1568:

• AC 1 — list with name, description, my internal role; groups without membership do not appear (target).
• AC 4 — plain member can self-remove but performs no management actions (target).
• AC 5 — org-group rows show membership-appropriate actions only, no owner-equivalent admin controls (structural placeholder).

Technical Notes

• Consume existing beans GroupInformationService / GroupService (already wired in datamanager-app AppConfig).
• Intentionally partial: AC 2/3 and functional AC 5 are NOT delivered here → Task B (backend FAEAT-USER-GROUPS-04/[Story] FEAT-USER-GROUPS-04: Manage Ad-hoc Group Membership and Profile (owner/manager) #1562) / Task C (org groups [Story] FEAT-USER-GROUPS-01: Create Org Groups (Admin) #1559/[Story] FEAT-USER-GROUPS-02: Manage Org Group Membership and Managers (Admin) #1560).
• PR must use Related to #1568, not Closes #1568; leave [Story] FEAT-USER-GROUPS-10: My Groups View (account area) #1568 OPEN and post a partial-progress comment after merge.
• Governance: GROUP-* requirement IDs are draft proposals pending the requirements PR (AGENTS.md §12); same precedent as PR [Story] FEAT-USER-GROUPS-03: Create Ad-hoc Groups Self-Service (backend) #1574 (implementation proceeded on PO direction).