test(10-03): add failing specs + real DÖE fixtures for adapter/normalizer

- Capture real, trimmed DÖE day-export fixtures (pubDay=2026-07-19, 8
  notices spanning tender/award/planning/untagged-with-awards tag classes)
  under tenders/__fixtures__/, live-downloaded from oeffentlichevergabe.de
- Define RawTenderRecord/NormalizedTenderFields/SourceType (tender.types.ts)
  and TenderSourceAdapter (day-cursor fetchTenders signature per RESEARCH
  Pattern 1)
- RED: doe-opendata.adapter.spec.ts asserts D-02 exact-count filtering,
  HTTP-400 no-op, and a zip-bomb ceiling guard (T-10-07)
- RED: tender-normalizer.service.spec.ts asserts eForms-primary deadline
  recovery where OCDS is null (RESEARCH Pattern 3), nullable deadline/value,
  dedupKey priority (ocid -> sourcePortal:sourceNoticeId), and a stable
  sha256 contentHash

apps/api/src/tenders/adapters/tender-source-adapter.interface.ts

@@ -0,0 +1,29 @@
+import type { RawTenderRecord, SourceType } from '../tender.types';
+
+/**
+ * Contract implemented by every tender source adapter (DÖE OpenData this
+ * phase; AI-NetServer/cosinex/RSS/email-alert in later phases).
+ *
+ * `fetchTenders` takes a day-cursor string (`YYYY-MM-DD`), NOT a `since: Date`
+ * timestamp — the DÖE OpenData API is a daily batch-export API with no
+ * incremental/since parameter (RESEARCH.md Pattern 1 corrects the
+ * `ARCHITECTURE.md` sketch's `since?: Date` signature). Day-cursor is kept
+ * as the shared interface shape so future adapters that ARE incremental
+ * (e.g. RSS) can still satisfy it by treating the day as a coarse filter,
+ * rather than forking the interface per source.
+ */
+export interface TenderSourceAdapter {
+  readonly sourceType: SourceType;
+
+  /**
+   * Fetch and lightly parse all open-tender ("tender"-tagged", D-02)
+   * notices for the given calendar day (Europe/Berlin), already filtered —
+   * implementations must NOT return award/planning/untagged-with-awards
+   * notices.
+   *
+   * @param dayCursor - `YYYY-MM-DD`, must be strictly in the past (today/
+   * future is rejected upstream by the DÖE API with HTTP 400). Implementations
+   * treat that 400 as an expected no-op and resolve to `[]`, never throw.
+   */
+  fetchTenders(dayCursor: string): Promise<RawTenderRecord[]>;
+}