Add per-module Gettext backend for sidebar tab labels

[timujinne]

Summary

• Adds PhoenixKitCRM.Gettext backend (lib/phoenix_kit_crm/gettext.ex) — module owns its own translation catalogue.
• All 4 Tab.new! registrations in lib/phoenix_kit_crm.ex (3 admin + 1 settings) declare gettext_backend: PhoenixKitCRM.Gettext.
• Pre-existing gettext() wrappers around Tab labels stripped to plain strings — the wrappers translated at registration time against whatever process locale was active during boot (wrong behaviour). Now Tab.localized_label/1 resolves at request time per the user's locale.
• All 4 internal-translation files swapped from PhoenixKitWeb.Gettext to PhoenixKitCRM.Gettext: phoenix_kit_crm.ex, web/column_modal.ex, column_config.ex, web/cell_format.ex. Once published, this module no longer depends on the parent app's gettext backend for its own UI strings.
• Translation catalogues for en, ru, et shipped under priv/gettext/<locale>/LC_MESSAGES/default.po — 19 unique msgids covering Tab labels and the gettext() calls auto-extracted from column_modal.ex / cell_format.ex.

CRM was the most complex module in the per-module-i18n rollout — pre-existing PhoenixKitWeb.Gettext references in 4 files plus gettext() wrappers around static Tab labels. Both concerns are addressed in this PR.

Behaviour matrix

phoenix_kit resolution	Sidebar tab labels	Internal CRM strings	i18n tests
Currently published (≤ 1.7.105)	raw English (graceful — gettext_backend: field silently dropped by Tab.new)	translated via PhoenixKitCRM.Gettext (locale plug already in effect)	excluded
Future release that ships PR #522 API	translated per user locale	translated per user locale	run automatically

Files (14)

M  CHANGELOG.md                                # +0.2.2 entry
M  mix.exs                                     # +:gettext app/dep, +priv in package files, @version 0.2.2
M  mix.lock
A  lib/phoenix_kit_crm/gettext.ex              # Gettext.Backend
M  lib/phoenix_kit_crm.ex                      # Tab labels stripped + gettext_backend on every Tab.new! (4 sites); host-app use Gettext removed
M  lib/phoenix_kit_crm/column_config.ex        # PhoenixKitWeb.Gettext → PhoenixKitCRM.Gettext (incl. explicit Gettext.gettext call)
M  lib/phoenix_kit_crm/web/column_modal.ex     # PhoenixKitWeb.Gettext → PhoenixKitCRM.Gettext
M  lib/phoenix_kit_crm/web/cell_format.ex      # PhoenixKitWeb.Gettext → PhoenixKitCRM.Gettext
A  priv/gettext/default.pot                    # 19 msgids (3 Tab + 16 from column_modal/cell_format)
A  priv/gettext/en/LC_MESSAGES/default.po      # en (1:1)
A  priv/gettext/ru/LC_MESSAGES/default.po      # ru (full)
A  priv/gettext/et/LC_MESSAGES/default.po      # et (Tab labels translated; column_modal/cell_format strings fall back to English msgid)
A  test/phoenix_kit_crm/i18n_test.exs          # 4 smoke assertions
M  test/test_helper.exs                        # conditional :requires_phoenix_kit_i18n_api skip

Translations (Tab labels — full set)

msgid	ru	et
CRM	CRM	CRM
Overview	Обзор	Ülevaade
Organizations	Организации	Organisatsioonid

CRM stays as "CRM" in all locales — industry acronym, not translated. Plus 16 additional msgids from gettext() calls in column_modal.ex and cell_format.ex (e.g. "Apply", "Cancel", "Customize columns", "Yes", "No") — fully translated to Russian; Estonian translations for those left as fallback-to-msgid where idiomatic translation was non-obvious.

Deliberately untouched

• lib/phoenix_kit_crm/web/settings_live.ex uses use PhoenixKitWeb, :live_view (host app's web module). The host web module injects Gettext, router helpers, and other compile-time macros at the host-app level; the package cannot and must not override that with its own backend. Migrating this file would break runtime translations for host apps that haven't configured PhoenixKitCRM.Gettext. Left as-is — this is intentional, not an oversight.
• lib/phoenix_kit_crm/sidebar_bootstrap.ex builds %Tab{label: role.name} (a runtime user-supplied string) for dynamic role tabs. Adding gettext_backend: here would be meaningless — there's no static msgid to look up; the role name is whatever the operator named it. Left as-is — Tab.localized_label/1 correctly returns the raw label when no backend is set, so dynamic labels render verbatim.

Test plan

• mix test with phoenix_kit resolved to PR #522 branch via path: override — i18n tests + module's existing tests, all pass.
• mix test with phoenix_kit resolved to currently published 1.7.105 — i18n tests excluded automatically; other tests unaffected.
• mix.exs package files: includes priv — .po files will ship to Hex consumers.
• Tab labels are now plain strings (no gettext() wrappers); gettext_backend: field set on each.
• grep -rn "use Gettext, backend: PhoenixKitWeb.Gettext" lib/ returns zero in committed form.
• CI re-verification on this PR.
• Maintainer review.