feat(investment,reconciliation): add Export to Excel across Investment, fix export popup

Adds a shared Export to Excel utility (investment-export.ts) and wires it
into every listing/report screen in the Investment module — Dashboard
(break-up + allocation), Reports (all ~20 report shapes), Interest (per
active tab), the FD/Bond/Share Holdings registers, and Masters (per active
master tab). Entry/transaction forms intentionally have no export button.
No sign-off is included here, matching the request to keep that feature
reconciliation-only.

Also fixes the Reconciliation export flow: the Prepared/Checked/Approved
sign-off is now an optional one-off popup shown when "Export to Excel" is
clicked (fields are blank by default and downloading works whether or not
they're filled), replacing the earlier always-visible sign-off card. Also
fixes three reconciliation reports (Sundry Dr/Cr, NEFT/RTGS, UDIR) whose
labels contain "/" — an Excel-forbidden worksheet-name character — which
was silently aborting their export.

src/app/investment/investment-reports/investment-reports.component.html

@@ -16,6 +16,11 @@
         same holdings/transactions used by the Entry screens.
       </p>
     </div>
+    <div class="pg-toolbar">
+      <button type="button" class="pg-btn pg-btn--ghost" [disabled]="generating" (click)="exportExcel()">
+        {{ generating ? 'Exporting…' : 'Export to Excel' }}
+      </button>
+    </div>
   </header>
 
   <div class="cctr-tabs">
@@ -692,3 +697,5 @@
     </div>
   }
 </div>
+
+<div class="inv-toast" [class.show]="toastVisible">{{ toastMsg }}</div>