feat: add investment and redemption functionality for hedge funds

- Implemented POST endpoint for investing in hedge funds, allowing users to invest a specified amount and receive shares based on the fund's NAV.
- Implemented POST endpoint for redeeming shares in hedge funds, enabling users to redeem shares for cash based on the current NAV.
- Created InvestPanel component for user interactions, including investing and redeeming shares, displaying current NAV, user balance, and holdings summary.

prisma/schema.prisma

@@ -26,21 +26,39 @@ model User {
   passwordResets PasswordReset[]
   managedFunds   FundManager[]
   fund           HedgeFund?
+  fundInvestments FundInvestment[]
 }
 
 model HedgeFund {
-  id        String        @id @default(cuid())
-  name      String        @unique
-  slug      String        @unique  // lowercase, URL-safe
-  userId    String        @unique  // shadow User account that holds positions/trades/balance
-  user      User          @relation(fields: [userId], references: [id])
-  createdAt DateTime      @default(now())
+  id                String        @id @default(cuid())
+  name              String        @unique
+  slug              String        @unique  // lowercase, URL-safe
+  userId            String        @unique  // shadow User account that holds positions/trades/balance
+  user              User          @relation(fields: [userId], references: [id])
+  sharesOutstanding Float         @default(0)  // total fund shares currently in circulation
+  createdAt         DateTime      @default(now())
 
-  managers  FundManager[]
+  managers    FundManager[]
+  investments FundInvestment[]
 
   @@index([slug])
 }
 
+model FundInvestment {
+  id            String    @id @default(cuid())
+  fundId        String
+  fund          HedgeFund @relation(fields: [fundId], references: [id], onDelete: Cascade)
+  userId        String
+  user          User      @relation(fields: [userId], references: [id], onDelete: Cascade)
+  shares        Float     // fund shares held by this investor
+  avgNavAtBuy   Float     // NAV per share at time of purchase (for display only)
+  createdAt     DateTime  @default(now())
+  updatedAt     DateTime  @updatedAt
+
+  @@unique([fundId, userId])
+  @@index([userId])
+}
+
 model FundManager {
   id      String    @id @default(cuid())
   fundId  String