feat(home): multi-file upload + per-file analysis, drop tool grid

Home is now upload + analysis only. The page accepts multiple files in
one go, analyzes each independently, and renders findings grouped by
filename in bordered containers. The 3-section tool-card grid is gone —
discovery happens via the sidebar now.

Mechanics:
- file_uploader uses accept_multiple_files=True. Each file's findings
  cache in session_state["home_findings_by_file"] keyed by filename so
  removing a file via Streamlit's "x" button drops its findings too,
  and re-clicking Run only re-analyzes pending files.
- The first uploaded file is mirrored into the singular
  home_uploaded_{name,bytes,size} keys so tool pages continue to pick
  up an "active" upload through pickup_or_upload — no tool-page changes.
- New i18n keys: upload.intro_multi, upload.uploader_label_multi,
  upload.clear_results, upload.empty_state. upload.heading text is
  updated to "Upload one or more files to start" (EN + ES).

Dropped tests pinning the tool grid:
- TestHomeToolGridLocalization (test_chrome.py)
- test_home_tool_card_uses_es_name (test_smoke.py)
- TestLiteHomeGridBadges (test_lite_tier.py — locked-card lock-badge
  assertions; locking is still enforced per-tool-page via
  require_feature_or_render_upgrade)

2009 tests pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/gui/test_chrome.py

@@ -114,8 +114,8 @@ class TestLocalizedChrome:
         with_language(home_app, "es")
         home_app.run()
         text = collected_text(home_app)
-        # ``📤 Sube un archivo para empezar`` from the es pack.
-        assert "Sube un archivo" in text
+        # ``📤 Sube uno o más archivos para empezar`` from the es pack.
+        assert "Sube uno o más archivos" in text
 
 
 # ---------------------------------------------------------------------------
@@ -157,25 +157,3 @@ class TestQuitButtonRenders:
         assert "trabajo sin guardar" in text
 
 
-# ---------------------------------------------------------------------------
-# Tool cards use localized names on the home grid
-# ---------------------------------------------------------------------------
-
-class TestHomeToolGridLocalization:
-    """The home grid pulls tool display names through ``tool_name()`` in
-    ``tools_registry``. The Spanish pack provides translations for every
-    tool id; a regression in that wiring would make Spanish users see
-    English names. Pin a few representative ones."""
-
-    @pytest.mark.parametrize("needle", [
-        "Buscar duplicados",
-        "Limpiar texto",
-        "Estandarizar formatos",
-        "Corregir valores faltantes",
-        "Mapear columnas",
-    ])
-    def test_es_tool_name_on_home_grid(self, home_app, needle):
-        with_language(home_app, "es")
-        home_app.run()
-        text = collected_text(home_app)
-        assert needle in text, f"missing localized tool name {needle!r}"