feat(monitoring/site-mappings): globalize site_domain_mappings

Drop tenant scoping on site_domain_mappings now that the citation query
resolves mappings without tenant filtering. Add a unique index on
registrable_domain plus an updated_at column, and switch the dev-seed
upsert to use ON CONFLICT (registrable_domain). Adds a SiteDomainMapping
type to ops/domain for the upcoming console management UI.

server/migrations_monitoring/20260429110000_globalize_site_domain_mappings.up.sql

@@ -0,0 +1,24 @@
+UPDATE site_domain_mappings
+SET registrable_domain = LOWER(TRIM(registrable_domain)),
+    site_key = LOWER(TRIM(site_key)),
+    site_name = TRIM(site_name);
+
+DELETE FROM site_domain_mappings older
+USING site_domain_mappings newer
+WHERE older.registrable_domain = newer.registrable_domain
+  AND older.id < newer.id;
+
+DROP INDEX IF EXISTS idx_site_domain_mappings_lookup;
+
+ALTER TABLE site_domain_mappings
+    DROP COLUMN IF EXISTS tenant_id,
+    ADD COLUMN IF NOT EXISTS updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW();
+
+CREATE UNIQUE INDEX IF NOT EXISTS uk_site_domain_mappings_domain
+    ON site_domain_mappings(registrable_domain);
+
+CREATE INDEX IF NOT EXISTS idx_site_domain_mappings_active_domain
+    ON site_domain_mappings(registrable_domain) WHERE is_active = TRUE;
+
+CREATE INDEX IF NOT EXISTS idx_site_domain_mappings_created
+    ON site_domain_mappings(created_at DESC, id DESC);