csv-parser: keep LLM-mapped tickers; don't pass them through T212 mapping

The route's resolve-slice loop is T212-specific — it looks tickers up
against the InstrumentMap, which only has T212's universe. For the LLM
path the ticker is already Yahoo-ready (e.g. VOD.L, ASML.AS), so
sending it through resolve_slice produced spurious "could not be
resolved" warnings and dropped the positions.

Fix: ParsedPie gains a ``tickers_resolved`` flag (default False for
T212 backward-compat); _apply_mapping in the LLM path sets it True
and also extracts currency from the LLM-mapped currency_col into a
new ``ParsedPosition.currency`` field. The route branches on the flag:
LLM-path positions are kept verbatim with a best-effort InstrumentMap
lookup for nicer name/currency overrides, never dropped.

Integration test tightened to assert all 5 IBKR fixture positions
round-trip with the right currencies (USD / GBP / EUR).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/services/llm_csv_parser.py

@@ -250,6 +250,7 @@ def _apply_mapping(
     qty_col = mapping["qty_col"]
     name_col = mapping.get("name_col")
     cost_col = mapping.get("cost_col")
+    currency_col = mapping.get("currency_col")
 
     positions: list[ParsedPosition] = []
     invested_total = 0.0
@@ -279,6 +280,9 @@ def _apply_mapping(
             name = row[idx[name_col]].strip()
         if not name:
             name = ticker
+        currency: str | None = None
+        if currency_col is not None and idx[currency_col] < len(row):
+            currency = row[idx[currency_col]].strip() or None
         positions.append(ParsedPosition(
             slice=ticker,
             name=name,
@@ -286,6 +290,7 @@ def _apply_mapping(
             current_value=None,
             result=None,
             quantity=qty,
+            currency=currency,
         ))
 
     return ParsedPie(
@@ -294,6 +299,7 @@ def _apply_mapping(
         invested=(invested_total if invested_seen else None),
         value=None,
         result=None,
+        tickers_resolved=True,
     )