feat(PROJ-12): E-Mail Export EML/PDF/ZIP

- GET /api/export/pdf/{id}: PDF-Generierung (stdlib, kein ext. Paket)
- POST /api/export/zip: Streaming-ZIP mit manifest.csv, Anhänge optional
- Max. 500 Mails pro Export, Zugriffscheck per Rolle
- Audit-Log für jeden Export
- Frontend: PDF-Button in Mail-Ansicht
- Frontend: Checkboxen + ZIP-Export-Dialog in Suchergebnissen

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

features/PROJ-12-export.md

@@ -1,8 +1,8 @@
 # PROJ-12: E-Mail-Export (EML / PDF)
 
-## Status: In Progress
+## Status: In Review
 **Created:** 2026-03-12
-**Last Updated:** 2026-03-13
+**Last Updated:** 2026-03-14
 
 ## Dependencies
 - Requires: PROJ-1 (Authentifizierung)
@@ -115,6 +115,33 @@ POST /api/export/zip
 | `archive/zip` (Stdlib) | Streaming-ZIP-Erstellung ohne externe Abhängigkeit |
 | `github.com/SebastiaanKlippert/go-wkhtmltopdf` | PDF-Generierung aus HTML (serverseitig) |
 
+## Implementation Notes (2026-03-14)
+
+### What was built
+
+**Go Backend — `internal/api/export.go` (new file):**
+- `GET /api/export/pdf/{id}` — generates a stdlib-only PDF (no external deps) using raw PDF 1.4 syntax with Helvetica core font. Renders header fields, plain-text body (with HTML-strip fallback), and attachment list. `toLatinSafe()` converts umlauts for Latin-1 compatibility.
+- `POST /api/export/zip` — streaming ZIP via `archive/zip` stdlib. Accepts `{"ids":[...], "attachments": true}`, max 500 IDs. Adds `{id[:16]}.eml`, optional `attachments/{id[:8]}/{filename}` entries, and `manifest.csv` (CSV with filename/message_id/from/to/subject/date). Audit-logged as `export: zip: N mails`.
+- Both handlers use `requireMailAccess` middleware (blocks admin role). RoleUser is filtered to own mails via `mailBelongsToUser`; RoleAuditor can export all.
+
+**Deviation from spec:** PDF generation uses a hand-rolled stdlib PDF writer instead of `go-wkhtmltopdf` or `go-pdf/fpdf` — avoids adding an external dependency that would require `go get` on the server.
+
+**Routes added to `internal/api/server.go`:**
+- `GET /api/export/pdf/{id}`
+- `POST /api/export/zip`
+
+**Frontend `src/lib/api.ts`:**
+- Added `exportMailPDF(id)` and `exportMailsZIP(ids, attachments)` export functions.
+
+**Frontend `src/app/mail/[id]/page.tsx`:**
+- Added "Als PDF exportieren" button next to "Als .eml herunterladen".
+
+**Frontend `src/app/search/page.tsx`:**
+- Added per-row Checkbox column + select-all header checkbox.
+- Export toolbar appears when ≥1 mail is selected.
+- ZIP export dialog with attachments toggle (Switch component).
+- Selection cleared when search results change.
+
 ## QA Test Results
 _To be added by /qa_