feat([issue-4188]): persist a universe's linked mood board on the record

[atomantic]

Summary

Phase 1 of #4188 (mood boards as a universe style-building tool): the universe record gains a persisted moodBoardId link, replacing the localStorage-only mood-board reference in the Universe Builder.

• Server — sanitizeTemplate accepts an optional moodBoardId pointer (mb-<uuid>, capped at MOOD_BOARD_ID_MAX), persisted only when set so existing records keep their on-disk shape. Accepted on create and PATCH (PATCHABLE_SCALARS); key-present with ''/null clears, key-absent preserves.
• Sync gate — universes schema version bumped 8 → 9. The pointer deliberately rides the wire (mood boards federate, so the id resolves on peers), and per the Structured character relationships + opposing-force tagging #1287/Object↔character emotional attachment / significance model #1288 precedent an additive wire-riding field must be version-gated or an older peer re-sanitizing the record would strip-then-LWW the link away. (The issue body guessed "no bump needed" — the codebase precedent says otherwise, so this deviates from the issue text there.) Hardcoded version fixtures in the sync/manifest tests updated. The field is hashed for conflict detection but not restorable — same treatment as mediaCollection.universeId (structural link).
• Client — MoodBoardReferenceStrip gains a controlled mode (value/onChange): selection is owned by the caller, never falls back to the first board (a deleted board shows as unset rather than silently drifting), and offers one-click create-and-link named after the universe (newBoardName). The Universe Bible tab drives it from the draft (draft.moodBoardId), persisted through the normal dirty-gated Save. Pipeline.jsx keeps the uncontrolled localStorage mode unchanged.

A codex review pass surfaced two P1s, fixed in the second commit:

• Behind-peer LWW strip — the version gate only rejects ahead senders, so a pre-v9 peer's edit is applied and its moodBoardId-unaware sanitized record would erase the local link. mergeUniversesFromSync now disambiguates omitted-vs-cleared by the sender's universes schema version (senderSchemaVersions, threaded from both the snapshot path in dataSync.applyRemote and the per-record push path in peerSyncReceive): a pre-v9/no-meta sender's omission preserves the local link; a v9-aware sender's omission is an explicit clear.
• Expand/refine auto-save — useUniverseExpand's create/update payloads omitted moodBoardId, so "Generate From Idea" on a new universe created it unlinked and rehydration silently dropped the pick.

Remaining phases of #4188 (gallery/upload pickers + video items, per-item prompt-from-media analysis, board→style synthesis) are not in this PR — see the reconciliation comment on the issue.

Refs #4188

Test plan

• server/services/universeBuilder.test.js — new moodBoardId suite: persists through create, absent when never set, PATCH set/preserve-on-absent/clear-on-''-and-null, non-string sanitized to absent on read; merge tests for behind-peer preserve, v9 explicit clear, and v9 apply-over-local.
• server/services/dataSync.pipelineUniverse.test.js — route-through test: a v8 sender's snapshot edit cannot strip moodBoardId, a v9 sender's omission clears it. peerSync.test.js call-args assertions extended with the threaded senderSchemaVersions.
• server/lib/schemaVersions.test.js + sync fixtures (dataSync.pipelineUniverse, peerSync, integration) updated for v9; ahead/behind gating asserted at v10-vs-v9.
• client/src/components/moodBoard/MoodBoardReferenceStrip.test.jsx — new: uncontrolled fallback + localStorage persistence unchanged; controlled mode no-fallback, onChange routing, no localStorage writes, deleted-board-shows-unset, create-and-link (with and without existing boards).
• Full server suite (Vitest, node) and full client suite (Vitest, jsdom) pass locally; biome lint clean.