Initial implementation of generic Excel-to-DB import tool

Supports .xls and .xlsx, Oracle and PostgreSQL via SQLAlchemy.
Includes CLI (run/inspect/generate-config), YAML config, auto schema
detection, and append/replace/upsert modes.

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

examples/import_config.yaml

@@ -0,0 +1,40 @@
+# SQLAlchemy DSN — Beispiele:
+#   PostgreSQL:  postgresql+psycopg2://user:pass@localhost/mydb
+#   Oracle:      oracle+oracledb://user:pass@localhost:1521/?service_name=MYDB
+dsn: "postgresql+psycopg2://user:pass@localhost/mydb"
+
+default_varchar_length: 255
+
+sheets:
+  - sheet: "Artikel"           # Sheet-Name oder Index (0, 1, ...)
+    header_row: 0              # 0-basierter Zeilenindex der Kopfzeile
+    skip_rows: 0               # Zeilen vor der Kopfzeile überspringen
+    target_table: "artikel"
+    mode: "replace"            # append | replace | upsert
+    upsert_keys: []
+    columns:
+      - source: "Artikelnummer"
+        target: "artikelnummer"
+        dtype: "VARCHAR(50)"
+      - source: "Bezeichnung"
+        target: "bezeichnung"
+      - source: "Preis"
+        target: "preis"
+        dtype: "NUMERIC(12,2)"
+      - source: "Interne Notiz"
+        target: "interne_notiz"
+        skip: true             # Spalte nicht importieren
+
+  - sheet: "Kunden"
+    header_row: 0
+    target_table: "kunden"
+    mode: "upsert"
+    upsert_keys: ["kundennummer"]
+    columns:
+      - source: "Kundennummer"
+        target: "kundennummer"
+        dtype: "VARCHAR(20)"
+      - source: "Name"
+        target: "name"
+      - source: "E-Mail"
+        target: "email"