feat(fase-9): wire sync_conflicts table + queue logging + debug panel

Closes 9.3 in full: migration 016 + pgTAP test 010 + queue.ts
conflict-detection path + /settings debug panel + integration test.

- Migration 016 adds public.sync_conflicts (append-only audit log of
  last-write-wins conflicts surfaced by the offline mutation queue).
  RLS allows owners to SELECT + INSERT their own rows only; UPDATE
  and DELETE have no policy and are silently denied. collective_id
  is intentionally nullable so user-level conflicts (theme, language
  in future) also fit. Indexed on (user_id, created_at desc) for the
  "show me my last 20 conflicts" query.
- queue.ts gains a `QueueContext` (currentUserId + collectiveId) and
  an optional `preImage` field on UpdateOp. Before sending an UPDATE
  the queue fetches the remote row (limited to the patched fields),
  proceeds with the UPDATE (last-write-wins), then fires a best-effort
  INSERT into sync_conflicts when the remote diverged. Failure to log
  never blocks the UPDATE or pollutes the pending_ops queue. Three
  unit specs (SC-01..SC-03) lock the contract in.
- sync/index.ts exposes setSyncContext(), called from (app)/+layout's
  $effect whenever currentUser / currentCollective change.
- New SyncConflictsPanel.svelte renders the last 20 conflict rows
  for the current user with an "Export JSON" button. Gated on
  import.meta.env.DEV (or a forceShow prop for a future secret
  unlock) — never ships in the production bundle. Slotted into
  /settings just above the Account section.
- Integration tests (packages/test-utils/tests/sync-conflicts.test.ts,
  4 SC-INT specs) exercise the real PostgREST + RLS contract end-to-end
  with the existing seed users (Ana, Borja). Requires fake-indexeddb in
  the test-utils dev deps (queue's IDB shim).
- pgTAP test 010 covers structure, RLS reads/writes, ownership rejection,
  and the append-only invariant (UPDATE/DELETE return 0 rows).
- packages/types/src/database.ts adds the sync_conflicts table type.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

apps/web/messages/en.json

@@ -187,5 +187,8 @@
 	"settings_appearance": "Appearance",
 	"settings_theme_light": "Light",
 	"settings_theme_dark": "Dark",
-	"settings_theme_system": "System"
+	"settings_theme_system": "System",
+	"settings_sync_conflicts": "Sync conflicts",
+	"settings_sync_conflicts_empty": "No conflicts logged.",
+	"settings_sync_conflicts_export": "Export JSON"
 }

apps/web/messages/es.json

@@ -187,5 +187,8 @@
 	"settings_appearance": "Apariencia",
 	"settings_theme_light": "Claro",
 	"settings_theme_dark": "Oscuro",
-	"settings_theme_system": "Sistema"
+	"settings_theme_system": "Sistema",
+	"settings_sync_conflicts": "Conflictos de sincronización",
+	"settings_sync_conflicts_empty": "Sin conflictos registrados.",
+	"settings_sync_conflicts_export": "Exportar JSON"
 }