UI-006: Ignore Tags for Processing and Statistics

Background

Processing could already be restricted to specific tags (TAGS + PROCESS_PREDEFINED_DOCUMENTS), but there was no way to explicitly exclude tags.

This is required for many workflows, for example when documents with specific markers should never be processed automatically.

views/setup.ejs
Added a new Ignore Tags input field.
Values are stored as CSV in ignoreTags.
views/settings.ejs
Added a new Ignore Tags input field.
Values are stored as CSV in ignoreTags.
public/js/setup.js
Extended the tag manager to also handle the ignore-tag list.
public/js/settings.js
Initialized an additional TagsManager for ignore tags.
routes/setup.js
Setup/Settings GET: loaded IGNORE_TAGS and normalized it as an array.
Setup/Settings POST: processed ignoreTags and persisted it as IGNORE_TAGS.
Dashboard: switched document count to effectively processable documents.
services/paperlessService.js
Added include/exclude tag helpers (parseTagList, resolveTagIdsByName, filterDocumentsByExcludedTagIds).
getAllDocuments() now also filters by IGNORE_TAGS.
Added getEffectiveDocumentCount() (for dashboard statistics).
config/config.js
Added ignoreTags sourced from IGNORE_TAGS.
tests/test-ignore-tags-filter.js
Added tests for include+exclude, exclude-only, and no-exclude.

node tests/test-ignore-tags-filter.js

Additionally verified manually: