Closes#850
## Summary
On `/zeitstrahl`, a curated event that has letters linked to it now renders as a contained event card — the event is the card header (accent glyph, title, `{date} · {kuratiert|abgeleitet}` subtitle, count, and a curator edit link), with its linked letters listed inside (first 5, then a keyboard-operable show-more/less toggle). Letters in a year *other* than the event's band get a lighter cross-year `✉ title` card. Every other letter stays a plain, alternating, density-folding chronological letter. There is **no grouping control** — clustering is automatic and always on. The meta-line drops its `Gruppierung: Datum` segment.
This supersedes #827: it keeps that branch's event-card clustering and the computed `linkedEventId`, and drops the toggle, the Thema mode, and the "Weitere Briefe" drawer.
## What changed
**Backend**
- `TimelineEntryDTO` gains a nullable `linkedEventId` (UUID; not `@Schema(REQUIRED)`).
- `TimelineService.resolveLetterEventLinks` resolves each letter's curated event in one batched pass over the events it already loads — no per-letter query, no new column, no Flyway migration.
- Regenerated the single `linkedEventId?` field in `api.ts`.
**Frontend**
- New `eventClustering.ts` (`buildEventLookup`, `splitYearLetters`, `CLUSTER_PREVIEW=5`) — filter-then-cluster: a letter clusters only if its `linkedEventId` is set AND present in the lookup, otherwise it stays loose.
- New `EventCluster.svelte` — the contained event card (same-year event header + edit link, or cross-year ✉ text header; first-5 + show-more).
- `LetterCard.svelte` gains `compact` + `variant='event'` (the `.lcard.ev` in-card letter).
- `YearBand.svelte` rebuilt to render event clusters inline; loose letters keep the alternating layout and density strip, and the strip counts **only** loose letters (no duplication).
- `TimelineView.svelte` builds the event lookup once and threads it + `canWrite` to each band.
- `+page.svelte` drops the grouping meta segment; the unused `timeline_grouping_date` key removed from de/en/es.
- New `timeline_bucket_show_more`/`_less` keys in all locales.
- REQ-010 `{@html}` grep gate over `lib/timeline/`.
## Tests (real runs)
- Backend `TimelineServiceTest`: **30 passed** (incl. the 2 new `linkedEventId` tests); `DerivedEventsAssemblyTest`: 17 passed; backend main sources compile.
- Frontend client sweep (`LetterCard`, `EventCluster`, `YearBand`, `TimelineView`, `zeitstrahl/page`): **81 passed** (5 files).
- Frontend server sweep (`eventClustering`, `messages`, `timeline-no-raw-html`): **18 passed** (3 files).
- `svelte-check`: no new errors in the touched files (pre-existing baseline noise elsewhere unchanged).
RTM: thirteen `REQ-001..013` rows added for #850 (feature `inline-event-clustering`), Status Done.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-authored-by: Marcel <marcel@familienarchiv>
Reviewed-on: #851
timeline_layer_* and timeline_derived_* shipped German values in the
English and Spanish catalogs, so EN/ES screen-reader users heard German
for the world/family layer and birth/death/marriage cues. Translate them;
de.json stays canonical.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
getAccentConfig(entry) maps each EVENT to its glyph (* / † / ⚭ / ★ / ◍), German
redundant-cue label, and accent kind (REQ-007/008/018). test-factories build
TimelineEntryDTO/TimelineDTO mirroring the real wire shape for component specs.
Refs #779
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
