feat: interface PIN, bulk disposition tagging, Google Drive delta scan, OCR memory fixes

- Interface PIN: optional session-level auth gate for the main scanner UI
  (Settings → Security → Interface PIN). Salted SHA-256 in config.json,
  rate-limited (5 attempts/5 min per IP). /view and viewer auth exempt.
  New /login page, before_request hook, GET/POST/DELETE /api/interface/pin,
  POST /api/interface/pin/verify, POST /api/interface/logout.

- Bulk disposition tagging: Select mode (filter bar "Vælg" button) reveals
  per-card checkboxes. Bulk tag bar at bottom of grid; POST /api/db/disposition/bulk.
  Disposition stats bar (total · unreviewed · retain · delete · % reviewed)
  updates after every save.

- Google Drive delta scan: uses Drive Changes API when delta is enabled.
  Per-user token stored as gdrive:{email} in delta.json. Load-then-merge
  save avoids racing with concurrent M365 token writes.

- PDF OCR OOM fix: render one page at a time with convert_from_path
  (first_page=N, last_page=N). Added _ocr_mem_ok() psutil guard (500 MB
  threshold) before each page render across scan_pdf, redact_fitz_pdf,
  redact_pdf.

- Email test message translation fix: routes/email.py returns structured
  {ok, method, recipients} instead of a hardcoded English string;
  scheduler.js builds the translated message client-side.

- Docs: CHANGELOG, README, TODO, MANUAL-EN, MANUAL-DA all updated.
  Lang files (en/da/de) extended with bulk, interface PIN, and SMTP keys.

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

lang/en.json

@@ -669,7 +669,23 @@
   "m365_smtp_test": "Test",
   "m365_smtp_testing": "Sending test email…",
   "m365_smtp_test_ok": "Test email sent",
+  "m365_smtp_test_ok_graph": "Test email sent via Microsoft Graph to",
+  "m365_smtp_test_ok_smtp": "Test email sent via SMTP to",
+  "m365_smtp_graph_also_failed": "(⚠ Graph also failed — Mail.Send not granted)",
   "m365_smtp_test_fail": "Connection failed",
+  "bulk_select_mode": "Select",
+  "bulk_select_all": "Select all visible",
+  "bulk_deselect_all": "Deselect all",
+  "bulk_apply": "Apply",
+  "bulk_done": "Done",
+  "bulk_selected": "selected",
+  "bulk_applied": "updated",
+  "disp_stats_total": "total",
+  "disp_stats_unreviewed": "unreviewed",
+  "disp_stats_retain": "retain",
+  "disp_stats_delete": "delete",
+  "disp_stats_other": "other",
+  "disp_stats_reviewed": "reviewed",
   "m365_fsrc_edit_btn": "Edit",
   "m365_fsrc_save_changes": "Save changes",
   "m365_settings_tab_scheduler": "Scheduler",
@@ -793,5 +809,19 @@
   "viewer_pin_saving": "Saving\u2026",
   "viewer_pin_saved": "PIN saved",
   "viewer_pin_clear_confirm": "Remove the viewer PIN? /view will require a token link again.",
-  "viewer_pin_cleared": "PIN cleared"
+  "viewer_pin_cleared": "PIN cleared",
+
+  "interface_pin_group_title": "Interface PIN",
+  "interface_pin_desc": "A numeric PIN (4\u20138 digits) that must be entered before accessing the main scanner interface. Viewers accessing <code style=\"font-size:10px\">/view</code> are not affected.",
+  "interface_pin_clear": "Clear PIN",
+  "interface_pin_is_set": "Interface PIN is set",
+  "interface_pin_not_set_msg": "No PIN set \u2014 interface is open to anyone on the network",
+  "interface_pin_saved": "PIN saved",
+  "interface_pin_clear_confirm": "Remove the interface PIN? The scanner will be accessible to anyone on the network.",
+  "interface_pin_cleared": "PIN cleared",
+  "interface_pin_login_desc": "Enter the interface PIN to continue.",
+  "interface_pin_login_btn": "Continue",
+  "interface_pin_err_incorrect": "Incorrect PIN.",
+  "interface_pin_err_too_many": "Too many attempts. Try again later.",
+  "interface_pin_err_network": "Network error. Please try again."
 }