perf(events): aggregate past UTC dates in one pass

[seonghobae]

Summary

• rebuilds the still-valuable server-side portion of ⚡ Bolt: 불필요한 배열 할당 및 Date 파싱 최적화 (성능 개선) #399 on the exact current developmental base;
• adds collectPastUtcDates under the server library boundary instead of keeping date bucketing inline in the route;
• replaces chained map → filter → map cache-invalidation transforms with one deterministic pass;
• returns Date[] directly for Prisma invalidation instead of serializing to ISO and reparsing;
• adds focused tests for first-seen ordering, UTC deduplication, current/future exclusion, timezone boundary behavior, leap-day preservation, and invalid timestamp handling.

Replacement scope

This is the canonical current-base owner for the API-route delta from #399. The chart-side date parsing work is owned by #425/#440 and is not included here. PR #447 was closed as a duplicate after this stronger package-level implementation was identified.

Behavior contract

• invalid timestamps are skipped, preventing invalid Date values from reaching Prisma;
• duplicate timestamps on the same UTC day collapse while preserving first-seen day order;
• the current UTC day and future UTC days are excluded;
• non-UTC source offsets are interpreted by the represented instant, matching the prior getUTC* date-bucketing semantics;
• no client timeline, dependency, lockfile, workflow, or bot-journal changes are included.

Exact-head gate

Current exact head: 3d9cf24865297335f81f8f65724403de7a64387b.

Merge only after exact-head CI, central OpenCode coverage evidence, SAST/Semgrep, Security Scan, dependency review, current-head review, zero unresolved actionable threads, and all live branch-protection rules pass. Queued, skipped, cancelled, stale, predecessor-head, status-only, or duplicate-PR evidence is not success.

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Configuration used: Organization UI

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Run ID: 4d06c0fb-5cfa-4964-b506-ddf94abd80dc

📥 Commits

Reviewing files that changed from the base of the PR and between 1c1a161 and 3d9cf24.

📒 Files selected for processing (3)

• packages/web/src/app/api/events/route.ts
• packages/web/src/lib/server/usage-date-buckets.test.ts
• packages/web/src/lib/server/usage-date-buckets.ts

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