feat: scan history browser, user-scoped viewer tokens, export fixes, email fixes (v1.6.20)

- Scan history browser (history.js, GET /api/db/sessions, get_sessions(),
  get_session_items(ref_scan_id)) — review any past session without rescanning
- User-scoped viewer tokens (#34) — scope by individual employee across M365
  and GWS; autocomplete from Accounts list; dual-email support
- Fix: GWS scan never marked finished (end_scan → finish_scan) and emitted
  wrong SSE event (scan_done → google_scan_done), excluding GWS items from all
  exports
- Fix: file scan begin_scan called with wrong keyword args (TypeError swallowed),
  so local/SMB items were never written to DB
- Fix: Graph sendMail reported failure on success — _post() now returns {} on
  empty 202 response instead of raising JSONDecodeError
- Fix: Graph error hidden behind generic "No SMTP host" message when both Graph
  and SMTP were unavailable
- Fix: Gmail vs Google Workspace SMTP error messages distinguished by username
  domain; Workspace errors point to admin console, not personal security settings
- Docs: update README, MANUAL-EN, MANUAL-DA, CLAUDE.md, TODO.md, CHANGELOG.md

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

lang/da.json

@@ -103,6 +103,13 @@
   "lbl_time": "Tid",
   "lbl_space": "Mellemrum",
   "lbl_loading": "Indlæser…",
+  "history_lbl": "Historik",
+  "history_items": "fund",
+  "history_btn_sessions": "Sessioner",
+  "history_btn_latest": "Seneste scanning",
+  "history_picker_empty": "Ingen tidligere scanninger",
+  "history_delta_badge": "Delta",
+  "history_latest_badge": "Seneste",
   "lbl_blurred": "Sløret",
   "lbl_none": "Ingen",
   "lbl_scanner": "Scanner",
@@ -766,8 +773,14 @@
   "share_create_error": "Kunne ikke oprette link:",
   "share_revoke_confirm": "Tilbagekald dette link? Alle der bruger det, mister straks adgang.",
   "share_revoke_error": "Kunne ikke tilbagekalde:",
-  "share_scope_lbl": "Rolleomfang",
-  "share_scope_all": "Alle roller",
+  "share_scope_lbl": "Omfang",
+  "share_scope_all": "Alle",
+  "share_scope_type_role": "Rolle",
+  "share_scope_type_user": "Bruger",
+  "share_scope_role_lbl": "Rolle",
+  "share_scope_user_lbl": "Brugerens e-mail",
+  "share_scope_user_placeholder": "alice@skole.dk",
+  "share_scope_user_invalid": "Angiv venligst en gyldig e-mailadresse for brugeromfanget.",
   "share_scope_staff": "Ansatte",
   "share_scope_student": "Elever",