feat(audit): overlapping evidence-slices fuer lueckenlose Beweiskette

Statt EIN full-page screenshot: full-page wird per PIL in viewport-grosse
Slices geschnitten, jede ueberlappt die vorherige um overlap_px Pixel.
Jeder Cookie erscheint in mind. einer Slice, an Slice-Grenzen sogar in
zwei → Dedup nach Name eliminiert die Doppel.

Warum nicht direkt scroll-based slicing in Playwright? VW's
Cookie-Page nutzt scroll-snap / fixed-position — alle viewport-shots
kamen identisch zurueck (Header-Overlay). PIL-cut auf dem full-page
PNG bypasst das Problem voellig.

VW smoke-test (32 slices):
  per-slice: [0, 0, 2, 5, 5, 3, 4, 7, 4, 3, 4, 5, ...]
  103 raw cookies → 79 unique nach dedup
  14 vendor records (Google 9, Adobe-Familie 17, etc.)

Jeder Slice hat eigenen Timestamp + SHA256 → ZIP-Anhang fuer
juristische Beweiskette.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

consent-tester/main.py

@@ -16,7 +16,10 @@ from services.consent_scanner import run_consent_test, ConsentTestResult
 from services.authenticated_scanner import run_authenticated_test, AuthTestResult
 from services.playwright_scanner import scan_website_playwright
 from services.dsi_discovery import discover_dsi_documents, DSIDiscoveryResult
-from services.page_screenshot import capture_page_evidence
+from services.page_screenshot import (
+    capture_page_evidence,
+    capture_page_overlapping_slices,
+)
 from checks.banner_runner import map_scan_to_checks
 
 logging.basicConfig(level=logging.INFO, format="%(levelname)s:%(name)s: %(message)s")
@@ -407,6 +410,59 @@ async def capture_evidence(req: EvidenceRequest):
     )
 
 
+# ── Evidence slices (overlapping scrolling screenshots) ─────────────
+
+class EvidenceSlicesRequest(BaseModel):
+    url: str
+    check_id: str = ""
+    viewport_h: int = 1024
+    overlap_px: int = 200
+    max_slices: int = 40
+
+
+class EvidenceSliceItem(BaseModel):
+    idx: int
+    ts: str
+    top_y: int
+    bot_y: int
+    sha256: str
+    png_b64: str
+    png_size: int
+
+
+class EvidenceSlicesResponse(BaseModel):
+    url: str
+    total_height_px: int
+    width_px: int
+    accepted_banner: bool
+    expanded: int
+    slices: list[EvidenceSliceItem]
+
+
+@app.post("/capture-evidence-slices", response_model=EvidenceSlicesResponse)
+async def capture_evidence_slices(req: EvidenceSlicesRequest):
+    """Overlapping viewport-screenshots fuer lueckenlose Beweiskette.
+
+    Jede Slice ueberlappt die vorherige um overlap_px Pixel — jeder Cookie
+    erscheint in mind. einem Bild, an Slice-Grenzen sogar in zwei. Dedup
+    nach Cookie-Name eliminiert die Doppel im Endresultat.
+    """
+    logger.info("Capturing overlapping evidence slices for %s", req.url)
+    data = await capture_page_overlapping_slices(
+        req.url, check_id=req.check_id,
+        viewport_h=req.viewport_h, overlap_px=req.overlap_px,
+        max_slices=req.max_slices,
+    )
+    return EvidenceSlicesResponse(
+        url=data["url"],
+        total_height_px=data["total_height_px"],
+        width_px=data["width_px"],
+        accepted_banner=data["accepted_banner"],
+        expanded=data["expanded"],
+        slices=[EvidenceSliceItem(**s) for s in data["slices"]],
+    )
+
+
 # ── Admin: CMP discoveries (Phase E) ────────────────────────────────
 
 @app.get("/cmp-discoveries")