feat(badge): support repeatable badges

[Armin1019]

Summary

• Badges get an IsRepeatable switch (default false, so every existing badge, including all Task Complete badges, stays one-time).
• Awarding: a repeatable badge is awarded again on every match and keeps one UserBadge record per award. Non-repeatable badges keep the existing "only once" check.
• The UserBadges (UserId, BadgeId) index is no longer unique (the auto-increment Id primary key already landed in AddIdToUserBadge #441).
• The app still sees one entry per badge: the badge list returns each badge once at its first award, badge detail and equip use the first award, and a repeat copy never takes a display slot. Display slots are now counted per badge, not per record. No app change.
• Migration AddIsRepeatableToBadge: adds Badges.IsRepeatable (bit, default 0), then drops and recreates IX_UserBadges_UserId_BadgeId without unique. No data is lost.

For reviewers

• Down recreates the unique index, so it fails once any user holds two copies of a badge. Dedupe by hand before rolling back.
• With the unique index gone, non-repeatable badges are only guarded in code. Two award runs at the same moment could both insert one (rare).
• A repeatable Task Complete badge is awarded on every completion, so ticking a task on and off could farm it. No badge is repeatable yet; pick its rule with care before switching one on.
• Staging cleanup (clearing user badges after deploy) is a manual SQL step for a tech lead. It is deliberately not in the migration, which also runs on Production.

Verified: dotnet test --filter "FullyQualifiedName~AwardNewBadgesToUserTests|FullyQualifiedName~GetUserBadgesTests|FullyQualifiedName~GetBadgeByIdTests|FullyQualifiedName~EquipBadgeTests" → 7 passed.

Release note

none

Status:

• User-facing — announce it
• Beta / partial — announce, but tagged as beta
• Hidden in production (feature-flagged / not enabled for users) — don't announce
• Internal only (refactor / infra / tests / CI / deps) — don't announce

[github-actions]

Test Results

155 tests   155 ✅  12s ⏱️
  1 suites    0 💤
  1 files      0 ❌

Results for commit f9b0afa.

♻️ This comment has been updated with latest results.

[github-actions]

Package	Line Rate	Branch Rate	Complexity	Health
BlotzTask	5%	37%	2983	❌
BlotzTask	5%	37%	2983	❌
Summary	5% (5522 / 120092)	37% (1190 / 3190)	5966	❌