docs(guide): add milestone release history (pre-pilot → pilot → production)

processes.gitea-issues: document the backfilled release timeline — 2026-02/03 pre-pilot,
2026-04/05 pilots, 2026-06 production go-live (17 June), 2026-07 current. Notes the
close-date scoping, the 100%-closed historical milestones, and the search-API pagination
gotcha (newest-first, ~200 cap).

backend/src/main/resources/content/processes/gitea-issues/overview.md

@@ -44,6 +44,25 @@ milestone gives a due date + automatic burndown (open/closed %).
 (the numeric id from the repo's milestone, not the title). Every fix we work gets assigned to its
 target release milestone.
 
+### Release history (backfilled 2026-07-05)
+The full closed-issue history is milestoned by **close date** — a continuous pre-pilot → pilot →
+production record. Each historical milestone is per-repo and **closed at 100%** (they represent
+completed releases, not plans):
+
+| Milestone | Issues | Stage |
+|---|---|---|
+| `2026-02` + `2026-03` | 5 + 22 | pre-pilot (early development) |
+| `2026-04` | 42 | April pilot |
+| `2026-05` | 83 | May pilot |
+| `2026-06` | 105 | **production go-live — 17 June 2026** |
+| `2026-07` | current | live release (in progress) |
+
+- Backfill was scoped to issues that **actually closed** in each month (by `closed_at`), not
+  "everything prior" — so each milestone reflects reality (a completed release), not a catch-all.
+- **Gotcha:** the search API returns newest-first and caps at ~200 results — **paginate**
+  (`&limit=50&page=N`) or older months get truncated (June's newer issues hid Feb–May on the first pass).
+- Rollup any release across repos: `GET /repos/issues/search?milestones=<YYYY-MM>&owner=hiveiq-src`.
+
 ## Assignment
 - **New issue** → assign `hiveiq` (triage / fix owner).
 - **Fix deployed** → reassign to the verifier and apply **`Verify Fix`**.