fix: use string budget in email service instead of float

The budget field is stored as a string (e.g., '$25-50'), not a number.
Updated EmailService.send_registration_confirmation() to accept budget
as a string and display it directly in the email.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/routes/participant.py

@@ -136,7 +136,7 @@ def register(slug: str):
                 magic_link_url=magic_link_url,
                 exchange_name=exchange.name,
                 exchange_description=exchange.description,
-                budget_amount=float(exchange.budget.replace("$", "")),
+                budget=exchange.budget,
                 gift_exchange_date=exchange.exchange_date.strftime("%Y-%m-%d"),
             )
         except Exception as e:

src/services/email.py

@@ -125,7 +125,7 @@ class EmailService:
         magic_link_url: str,
         exchange_name: str,
         exchange_description: str | None,
-        budget_amount: float,
+        budget: str,
         gift_exchange_date: str,
     ) -> Any:
         """Send registration confirmation email with magic link.
@@ -136,7 +136,7 @@ class EmailService:
             magic_link_url: Full URL with magic token
             exchange_name: Name of the exchange
             exchange_description: Description of the exchange (optional)
-            budget_amount: Budget amount
+            budget: Budget description (e.g., "$25-50")
             gift_exchange_date: Date of gift exchange
 
         Returns:
@@ -159,7 +159,7 @@ class EmailService:
                 {description_html}
                 <h3>Exchange Details</h3>
                 <ul>
-                    <li><strong>Budget:</strong> ${budget_amount:.0f}</li>
+                    <li><strong>Budget:</strong> {budget}</li>
                     <li><strong>Gift Exchange Date:</strong> {gift_exchange_date}</li>
                 </ul>
                 <h3>Access Your Dashboard</h3>