fix: clean up church-matcher types and add HK OSM bounding box

- Remove discovermassId/buscarmisasNetworkId from findDuplicateChurch match
  passes (importers now do their own pre-check dedup); restore as optional
  fields on ExistingChurch to keep type/runtime in sync
- Add HK bounding box to COUNTRY_BOUNDING_BOXES; fix silent 0-result
  fallback when country query returns empty from mirror server
- discovermass importer: add --limit flag and skip-already-imported
  pre-check using importedSlugs set
- Import scripts: remove discovermassId from ExistingChurch select/stubs
  (field not needed in shared matcher context)
- Schema: reorder discovermassId/kerknetId/gottesdienstzeitenId fields

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/import-osm-churches.ts

@@ -204,7 +204,6 @@ async function importFromOSM(countryCode: string, dryRun: boolean = false): Prom
         miserendId: true,
         kerknetId: true,
         gottesdienstzeitenId: true,
-      discovermassId: true,
         source: true,
         website: true,
         phone: true,
@@ -380,7 +379,6 @@ async function importFromOSM(countryCode: string, dryRun: boolean = false): Prom
             miserendId: null,
             kerknetId: null,
             gottesdienstzeitenId: null,
-            discovermassId: null,
             source: 'osm',
             website: osmChurch.website || null,
             phone: osmChurch.phone || null,