feat(investment): deal time, interest cycle and charges on Purchase Entry

As per Jitendra Sir's review:
- Deal Time is now a mandatory field next to Deal Date.
- New Interest Cycle section: the two coupon days, last and next coupon,
  next coupon amount and days to it.
- Stamp duty, brokerage and other charges sit on the main form. They are
  expenses on their own GLs (500601/500602/500603), so they are added to
  the settlement amount but no longer to the book value, and each shows
  as its own debit line in the accounting preview.

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

src/app/investment/bond-investment/bond-investment.component.ts

@@ -29,11 +29,16 @@ import {
   INVESTMENT_GL_BY_TYPE,
   INVESTMENT_GL_LOOKUP,
   INTEREST_RECEIVABLE_GL,
+  STAMP_DUTY_GL,
+  BROKERAGE_GL,
+  OTHER_CHARGES_GL,
   SETTLEMENT_BANK_GL_OPTIONS,
   periodBetween,
   parseDDMMYYYY,
   days360,
   lastHalfYearlyCouponDate,
+  nextHalfYearlyCouponDate,
+  couponDatesLabel,
   InvestmentHolding,
   InvestmentTxn,
   InstrumentType,
@@ -135,6 +140,7 @@ interface BondPurchaseForm {
   holdingDays: number | null;
   stampDuty: number | null;
   stampDutyAc: string;
+  otherCharges: number | null;
 }
 
 interface AccountingPreviewLine {
@@ -448,7 +454,8 @@ export class BondInvestmentComponent implements OnInit {
       nav: null,
       holdingDays: null,
       stampDuty: null,
-      stampDutyAc: ''
+      stampDutyAc: '',
+      otherCharges: null
     };
   }
 
@@ -518,14 +525,41 @@ export class BondInvestmentComponent implements OnInit {
     return this.isMutualFund ? this.purchaseForm.nav || 0 : 100;
   }
 
-  /** Book Value — what the investment is carried at, i.e. amount actually paid. */
+  /** Book Value — the price paid for the security. Charges are expenses and stay out of it (Jitendra Sir). */
   get purchaseBookValue(): number {
     const f = this.purchaseForm;
     if (this.isMutualFund) {
-      return this.purchaseBaseAmount + (f.stampDuty || 0) + (f.brokerage || 0);
+      return this.purchaseBaseAmount;
     }
     const rate = f.purchaseRate || 100;
-    return Math.round((this.purchaseBaseAmount * rate) / 100) + (f.brokerage || 0);
+    return Math.round((this.purchaseBaseAmount * rate) / 100);
+  }
+
+  /** Stamp duty + brokerage + other charges — paid with the settlement, booked to expense GLs. */
+  get purchaseTotalCharges(): number {
+    const f = this.purchaseForm;
+    return (f.stampDuty || 0) + (f.brokerage || 0) + (f.otherCharges || 0);
+  }
+
+  // Interest cycle of the security being bought: its two coupon days and the next coupon after the deal.
+  get purchaseCouponDates(): string {
+    return this.purchaseMaturityDate ? couponDatesLabel(this.purchaseMaturityDate) : '';
+  }
+
+  get purchaseNextCouponDate(): string {
+    const f = this.purchaseForm;
+    return this.purchaseMaturityDate && f.dealDate
+      ? nextHalfYearlyCouponDate(this.purchaseMaturityDate, f.dealDate)
+      : '';
+  }
+
+  get purchaseNextCouponAmount(): number {
+    const f = this.purchaseForm;
+    return f.intRate ? Math.round((this.purchaseBaseAmount * f.intRate) / 200) : 0;
+  }
+
+  get purchaseDaysToNextCoupon(): number {
+    return this.purchaseNextCouponDate ? days360(this.purchaseForm.dealDate, this.purchaseNextCouponDate) : 0;
   }
 
   get purchaseYtm(): number {
@@ -574,9 +608,9 @@ export class BondInvestmentComponent implements OnInit {
     }
   }
 
-  /** Settlement Amt of Purchase — book value plus accrued interest payable to the seller. */
+  /** Settlement Amt of Purchase — book value, accrued interest payable to the seller and the charges. */
   get purchaseSettlementAmount(): number {
-    return this.purchaseBookValue + this.purchaseAccruedInterest;
+    return this.purchaseBookValue + this.purchaseAccruedInterest + this.purchaseTotalCharges;
   }
 
   get purchaseMaturityAmount(): number {
@@ -683,6 +717,28 @@ export class BondInvestmentComponent implements OnInit {
         amount: accrued
       });
     }
+    const f = this.purchaseForm;
+    for (const [
+      gl,
+      amount
+    ] of [
+      [
+        STAMP_DUTY_GL,
+        f.stampDuty
+      ],
+      [
+        BROKERAGE_GL,
+        f.brokerage
+      ],
+      [
+        OTHER_CHARGES_GL,
+        f.otherCharges
+      ]
+    ] as const) {
+      if (amount && amount > 0) {
+        lines.push({ side: 'Dr', glCode: gl.glCode, glName: gl.glName, amount });
+      }
+    }
     lines.push({ side: 'Cr', glCode: crGl, glName: this.glNameOf(crGl), amount: total });
     return lines;
   }
@@ -693,6 +749,7 @@ export class BondInvestmentComponent implements OnInit {
     if (!f.scriptCode) missing.push('Script Code');
     if (!f.partyCode) missing.push('Party Code');
     if (!f.dealDate) missing.push('Deal Date');
+    if (!f.dealTime) missing.push('Deal Time');
     if (this.isMutualFund) {
       if (!f.considerAmt) missing.push('Consider Amt');
       if (!f.nav) missing.push('NAV');
@@ -726,9 +783,11 @@ export class BondInvestmentComponent implements OnInit {
       dealTime: f.dealTime || '',
       settlementType: f.settlementType,
       ...(this.isMutualFund
-        ? { considerAmt: f.considerAmt, nav: f.nav, stampDuty: f.stampDuty ?? null }
+        ? { considerAmt: f.considerAmt, nav: f.nav }
         : { faceValue: f.faceValue, purchaseRate: f.purchaseRate, lastIntDate: f.lastIntDt }),
+      stampDuty: f.stampDuty ?? null,
       brokerage: f.brokerage ?? null,
+      otherCharges: f.otherCharges ?? null,
       category: f.category,
       crGlAccountId,
       subType: f.subType || '',