Backend module: CSV import for the VITEC domain models

New "VITEC Import" module under Web: one import page per domain model
(v1: Market, Solution, Product - registry-driven, adding a model is one
config entry). Workflow: upload a CSV (delimiter and encoding are
auto-detected, including German-Excel semicolon/Windows-1252), map CSV
columns to DB fields, persist the mapping per model together with the
identity field used for matching (new table tx_vitec_import_mapping,
no TCA - pure tool configuration), review a unified list of CSV rows
matched against the DB records (new / update with differing fields /
unchanged / db-only), then apply the checked rows through DataHandler.

Each importable row carries an editable JSON payload textarea - what
is written is the textarea content, not the raw CSV, so editors can
fix values right in the review step. The parsed CSV travels through
the form as a hidden JSON field: no session state, no temp files.
Importable fields are derived from TCA at runtime (scalar types only;
files, categories and other relations are excluded - a flat CSV
cannot carry them). Payloads are whitelisted against that field list
on apply; new records require a storage pid (prefilled from existing
records). BE user permissions apply via DataHandler.

Deliberately out of v1: import log with three-way compare (protection
against overwriting manual edits), images/relations, multiple saved
mappings per model.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

packages/vitec/ext_tables.sql

@@ -292,3 +292,15 @@ CREATE TABLE tx_vitec_form_submission (
     delivery_status varchar(20) DEFAULT '' NOT NULL,
     delivery_error text
 );
+
+CREATE TABLE tx_vitec_import_mapping (
+    uid int(11) NOT NULL auto_increment,
+    pid int(11) DEFAULT '0' NOT NULL,
+    tstamp int(11) DEFAULT '0' NOT NULL,
+    crdate int(11) DEFAULT '0' NOT NULL,
+    model varchar(64) DEFAULT '' NOT NULL,
+    identity_field varchar(64) DEFAULT 'slug' NOT NULL,
+    mapping text,
+    PRIMARY KEY (uid),
+    KEY model (model)
+);