security(escrow): add JwtAuthGuard to POST escrow/fund endpoint (#38)

[MyDude92]

🎯 Objective

Closes #38. Applies JwtAuthGuard to POST /escrow/fund in EscrowController, ensuring that only authenticated sponsors can initiate escrow funding and register funder payloads.

---

📊 Before vs. After Benchmark Matrix

Caller	Inbound Request	Legacy Behavior	Solved Guarded Behavior
Unauthenticated Bot	POST /escrow/fund	❌ Processed anonymously	401 Unauthorized (Blocked)
Authenticated Sponsor	POST /escrow/fund	Funded	Funded securely

---

🛠️ Precise Kernel Diff (src/escrow/escrow.controller.ts)

+  @UseGuards(JwtAuthGuard)
   @Idempotent('escrow.fund')
   @Post('fund')
   async fund(@Body() dto: FundEscrowDto) {

[vercel]

@MyDude92 is attempting to deploy a commit to the chonilius' projects Team on Vercel.

A member of the Team first needs to authorize it.