feat(teams): add opt-in /teamsync reposition to tidy existing team roles

Creation-time placement only positions NEW team roles. Team roles made before
divider placement existed (sitting at the bottom of the role list) stayed put.

Add `reposition_team_roles(guild)` and expose it via `/teamsync reposition:true`
(off by default, so the hourly task never reorders roles on its own). It moves
each EXISTING team role under its game's divider, sheet-driven:

- a role's game/divider comes from sheets.get_game_for_team;
- roles whose team is no longer in the sheet (or game unknown) are left alone;
- idempotent: a role already within its section band (below its own divider,
  above the next divider down) is skipped, so re-runs move nothing.

Adds RepositionSummary, TEAMSYNC_UI/OPT strings, and tests.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01R6JZkyszyDFuFtk25WBbcR

strings/member.py

@@ -113,4 +113,7 @@ TEAMSYNC_UI: dict[str, str] = {
     "no_changes":     "✨ Kõik tiimirollid olid juba korras.",
     "changes_header": "**Muudatused:**",
     "changes_more":   "... ja {count} rohkem",
+    "reposition_header": "**Ümberpaigutus:**",
+    "repositioned":   "📦 Ümber paigutatud rolle: {count}",
+    "reposition_none": "✨ Olemasolevad tiimirollid olid juba õiges sektsioonis.",
 }