feat(cmp): vendor-agnostic consent data model — 13 new fields

Extend banner consent records with consent_method, banner_version,
banner_config_hash, geo, page_url, referrer, device info, session_id
and consent_scope for full Art. 7 DSGVO proof with any tracking vendor.

Migration 107, backward-compatible (all fields nullable).
Admin detail modal shows tracking context, device info and technical data.
Fix pre-existing str|None → Optional[str] for Python 3.9 compat.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend-compliance/compliance/services/_banner_serializers.py

@@ -24,8 +24,22 @@ def consent_to_dict(c: BannerConsentDB) -> dict[str, Any]:
         "categories": c.categories or [],
         "vendors": c.vendors or [],
         "ip_hash": c.ip_hash,
+        "user_agent": c.user_agent,
         "consent_string": c.consent_string,
         "linked_email": c.linked_email,
+        "consent_method": c.consent_method,
+        "banner_version": c.banner_version,
+        "banner_config_hash": c.banner_config_hash,
+        "geo_country": c.geo_country,
+        "geo_region": c.geo_region,
+        "consent_scope": c.consent_scope,
+        "page_url": c.page_url,
+        "referrer": c.referrer,
+        "device_type": c.device_type,
+        "browser": c.browser,
+        "os": c.os,
+        "screen_resolution": c.screen_resolution,
+        "session_id": c.session_id,
         "expires_at": c.expires_at.isoformat() if c.expires_at else None,
         "created_at": c.created_at.isoformat() if c.created_at else None,
         "updated_at": c.updated_at.isoformat() if c.updated_at else None,