feat(investment): settle purchases from Holdings; broken-period interest to settlement date

- Purchases are saved as Pending Settlement. Holdings show the status and
  a Settle button (from the settlement date), and the GL transaction id
  once settled.
- The transaction log shows "Not posted (pending settlement)" until a
  deal is settled, and dates the purchase on its settlement date.
- Broken-period interest is counted up to the settlement date.
- Accounting Preview title and the Holdings Settlement Date column
  reflect settlement-date posting.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/investment/investment-data.ts

@@ -17,7 +17,7 @@
  */
 
 export type InstrumentType = 'FD' | 'GOVT_SECURITY' | 'NON_SLR' | 'BOND' | 'MUTUAL_FUND' | 'SHARE';
-export type HoldingStatus = 'ACTIVE' | 'MATURED' | 'SOLD' | 'WRITTEN_OFF';
+export type HoldingStatus = 'PENDING_SETTLEMENT' | 'ACTIVE' | 'MATURED' | 'SOLD' | 'WRITTEN_OFF';
 export type InterestFreq = 'MONTHLY' | 'QUARTERLY' | 'HALF_YEARLY' | 'YEARLY' | 'CUMULATIVE';
 export type TxnType =
   | 'PURCHASE'
@@ -133,6 +133,10 @@ export interface InvestmentHolding {
   partyCode?: string;
   bookValue?: number;
   settlementAmount?: number;
+  /** Settlement date of the deal (deal date + T+n) — it can be settled on or after this day. */
+  settlementDate?: string;
+  /** Journal entry transaction posted when the deal was settled. */
+  glTransactionId?: string;
 }
 
 export interface InvestmentTxn {