feat: HTML email report with hints + fix duplicate Social Media sections

1. Email report now renders as styled HTML (matching frontend design):
   - Progress bars (green=completeness, blue=correctness)
   - Hierarchical L1→L2 check display
   - Red hint boxes under failed checks explaining what to fix
   - Matched text evidence for passed checks

2. Section splitter deduplicates: two "Social Media" headings on the
   same page are merged into one section instead of creating duplicates.

3. Extracted report builder to agent_doc_check_report.py (175 LOC)
   to keep routes file under 500 LOC (386 LOC).

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

backend-compliance/compliance/api/agent_doc_check_report.py

@@ -0,0 +1,175 @@
+"""
+HTML email report builder for document checks.
+
+Generates a styled HTML report similar to the frontend ChecklistView,
+including L1/L2 check hierarchy, progress bars, and actionable hints.
+"""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from .agent_doc_check_routes import CheckItem, DocCheckResult
+
+
+def _bar(pct: int, color: str) -> str:
+    bg = {"green": "#22c55e", "yellow": "#eab308", "red": "#ef4444", "blue": "#60a5fa"}
+    c = bg.get(color, "#60a5fa")
+    return (
+        f'<div style="display:inline-block;width:120px;height:8px;background:#e5e7eb;'
+        f'border-radius:4px;overflow:hidden;vertical-align:middle;margin-right:8px">'
+        f'<div style="width:{pct}%;height:100%;background:{c};border-radius:4px"></div>'
+        f'</div><span style="font-size:13px;font-weight:600;color:{c}">{pct}%</span>'
+    )
+
+
+def _icon(passed: bool, skipped: bool = False) -> str:
+    if skipped:
+        return '<span style="color:#d1d5db">&mdash;</span>'
+    if passed:
+        return '<span style="color:#22c55e;font-weight:bold">&#10003;</span>'
+    return '<span style="color:#ef4444;font-weight:bold">&#10007;</span>'
+
+
+def _hint_box(hint: str) -> str:
+    return (
+        f'<div style="font-size:11px;color:#dc2626;margin:2px 0 4px 20px;'
+        f'padding:4px 8px;background:#fef2f2;border-radius:4px;'
+        f'border-left:3px solid #fca5a5">{hint}</div>'
+    )
+
+
+def build_html_report(
+    results: list[DocCheckResult],
+    cookie_result: dict | None,
+) -> str:
+    """Build HTML email report styled like the frontend."""
+    ok_count = sum(1 for r in results if r.completeness_pct == 100)
+    html = [
+        '<div style="font-family:-apple-system,BlinkMacSystemFont,sans-serif;'
+        'max-width:700px;margin:0 auto">',
+        '<h2 style="margin-bottom:4px">Dokumenten-Pruefung</h2>',
+        f'<p style="color:#6b7280;margin-top:0">'
+        f'{len(results)} Dokumente, {ok_count} vollstaendig</p>',
+    ]
+
+    for r in results:
+        _render_document(html, r)
+
+    if cookie_result:
+        _render_cookie_banner(html, cookie_result)
+
+    html.append('</div>')
+    return "\n".join(html)
+
+
+def _render_document(html: list[str], r: DocCheckResult) -> None:
+    pct = r.completeness_pct
+    cpct = r.correctness_pct
+    bar_color = "green" if pct >= 80 else "yellow" if pct >= 50 else "red"
+    status_label = "OK" if pct == 100 else "LUECKENHAFT" if pct >= 50 else "MANGELHAFT"
+    if r.error:
+        status_label = "FEHLER"
+
+    l1_checks = [c for c in r.checks if c.level == 1]
+    l2_by_parent: dict[str, list[CheckItem]] = {}
+    for c in r.checks:
+        if c.level == 2 and c.parent:
+            l2_by_parent.setdefault(c.parent, []).append(c)
+
+    l1_passed = sum(1 for c in l1_checks if c.passed)
+    l2_active = [c for c in r.checks if c.level == 2 and not c.skipped]
+    l2_passed = sum(1 for c in l2_active if c.passed)
+
+    # Header
+    html.append(
+        f'<div style="border:1px solid #e5e7eb;border-radius:8px;margin-bottom:12px;overflow:hidden">'
+        f'<div style="padding:12px 16px;background:#f9fafb">'
+        f'<div style="display:flex;justify-content:space-between;align-items:center"><div>'
+        f'<span style="font-size:11px;background:#f3f4f6;padding:2px 8px;border-radius:4px;'
+        f'color:#4b5563;font-weight:500;margin-right:8px">{status_label}</span>'
+        f'<strong style="font-size:14px">{r.label}</strong>'
+        f'<div style="font-size:12px;color:#6b7280;margin-top:2px">'
+        f'{l1_passed}/{len(l1_checks)} Pflichtangaben'
+    )
+    if l2_active:
+        html.append(f', {l2_passed}/{len(l2_active)} Detailpruefungen')
+    html.append(f'</div></div><div style="text-align:right">{_bar(pct, bar_color)}')
+    if cpct and l2_active:
+        html.append(f'<br>{_bar(cpct, "blue")}')
+    html.append('</div></div></div>')
+
+    # Body
+    if r.error:
+        html.append(f'<div style="padding:12px 16px;color:#991b1b">{r.error}</div>')
+    else:
+        html.append('<div style="padding:8px 16px 12px">')
+        for c in l1_checks:
+            _render_l1_check(html, c, l2_by_parent.get(c.id, []))
+        if r.word_count:
+            html.append(
+                f'<div style="font-size:11px;color:#9ca3af;margin-top:8px;'
+                f'padding-top:8px;border-top:1px solid #e5e7eb">'
+                f'{r.word_count} Woerter analysiert</div>'
+            )
+        html.append('</div>')
+    html.append('</div>')
+
+
+def _render_l1_check(
+    html: list[str], c: CheckItem, children: list[CheckItem],
+) -> None:
+    l2_sub = [ch for ch in children if not ch.skipped]
+    l2_passed = sum(1 for ch in l2_sub if ch.passed)
+
+    style = "color:#991b1b;font-weight:600" if not c.passed else "color:#374151"
+    html.append(
+        f'<div style="padding:3px 0">{_icon(c.passed)} '
+        f'<span style="font-size:13px;{style}">{c.label}</span>'
+    )
+    if l2_sub:
+        html.append(f' <span style="color:#9ca3af;font-size:11px">({l2_passed}/{len(l2_sub)})</span>')
+    if not c.passed and c.hint:
+        html.append(_hint_box(c.hint))
+    html.append('</div>')
+
+    for ch in children:
+        if ch.skipped:
+            continue
+        _render_l2_check(html, ch)
+
+
+def _render_l2_check(html: list[str], ch: CheckItem) -> None:
+    style = "color:#dc2626;font-weight:500" if not ch.passed else "color:#6b7280"
+    html.append(
+        f'<div style="padding:2px 0 2px 24px;border-left:2px solid #e5e7eb;margin-left:8px">'
+        f'{_icon(ch.passed)} '
+        f'<span style="font-size:12px;{style}">{ch.label}</span>'
+    )
+    if ch.passed and ch.matched_text:
+        html.append(
+            f'<div style="font-size:10px;color:#9ca3af;font-family:monospace;'
+            f'margin-left:20px;overflow:hidden;text-overflow:ellipsis;'
+            f'white-space:nowrap">"...{ch.matched_text[:80]}..."</div>'
+        )
+    if not ch.passed and ch.hint:
+        html.append(_hint_box(ch.hint))
+    html.append('</div>')
+
+
+def _render_cookie_banner(html: list[str], cookie_result: dict) -> None:
+    html.append(
+        '<div style="border:1px solid #e5e7eb;border-radius:8px;'
+        'padding:12px 16px;margin-bottom:12px">'
+        '<strong>Cookie-Banner Pruefung</strong><br>'
+        f'Banner erkannt: {cookie_result.get("banner_detected", False)}<br>'
+        f'Anbieter: {cookie_result.get("banner_provider", "unbekannt")}'
+    )
+    violations = cookie_result.get("banner_checks", {}).get("violations", [])
+    if violations:
+        for v in violations[:10]:
+            html.append(f'<br>{_icon(False)} {v.get("text", "")[:80]}')
+    else:
+        html.append('<br><span style="color:#22c55e">Keine Verstoesse erkannt.</span>')
+    html.append('</div>')