Add Terms and Conditions and marketing opt-in checkboxes to registration

Registration now requires agreeing to the Terms and Conditions and lets
users opt in to hear about future projects. The opt-in is persisted on
the user via a new marketing_opt_in column (migration included).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/Tech/Entity/User.php

@@ -39,6 +39,9 @@ class User implements UserInterface, PasswordAuthenticatedUserInterface
     #[ORM\Column(type: 'boolean')]
     private bool $isVerified = false;
 
+    #[ORM\Column(type: 'boolean')]
+    private bool $marketingOptIn = false;
+
     public function getId(): ?int
     {
         return $this->id;
@@ -137,4 +140,16 @@ class User implements UserInterface, PasswordAuthenticatedUserInterface
 
         return $this;
     }
+
+    public function isMarketingOptIn(): bool
+    {
+        return $this->marketingOptIn;
+    }
+
+    public function setMarketingOptIn(bool $marketingOptIn): static
+    {
+        $this->marketingOptIn = $marketingOptIn;
+
+        return $this;
+    }
 }