feat(db): add project personas and skills tables

* Introduce project_personas table with foreign keys to projects and agent_personas
* Add project_skills table with foreign key to projects and agent_skills
* Include override boolean field in agent_persona_skills and project_skills
* Update schema and migration files to reflect new tables and fields
* Enhance CORS handling to reflect request origin

schema/agent_personas.dbml

@@ -43,6 +43,7 @@ Table agent_persona_skills {
   id bigserial [pk]
   persona_id bigint [not null, ref: > agent_personas.id]
   skill_id bigint [not null, ref: > agent_skills.id]
+  override boolean [not null, default: false]
 
   indexes {
     (persona_id, skill_id) [uk]
@@ -50,6 +51,19 @@ Table agent_persona_skills {
   }
 }
 
+Table project_personas {
+  id bigserial [pk]
+  project_id bigint [not null, ref: > projects.id]
+  persona_id bigint [not null, ref: > agent_personas.id]
+  is_default boolean [not null, default: false]
+  created_at timestamptz [not null, default: `now()`]
+
+  indexes {
+    (project_id, persona_id) [uk]
+    project_id
+  }
+}
+
 Table agent_persona_guardrails {
   id bigserial [pk]
   persona_id bigint [not null, ref: > agent_personas.id]
@@ -124,6 +138,8 @@ Ref: agent_persona_parts.persona_id > agent_personas.id [delete: cascade]
 Ref: agent_persona_parts.part_id > agent_parts.id [delete: cascade]
 Ref: agent_persona_skills.persona_id > agent_personas.id [delete: cascade]
 Ref: agent_persona_skills.skill_id > agent_skills.id [delete: cascade]
+Ref: project_personas.project_id > projects.id [delete: cascade]
+Ref: project_personas.persona_id > agent_personas.id [delete: cascade]
 Ref: agent_persona_guardrails.persona_id > agent_personas.id [delete: cascade]
 Ref: agent_persona_guardrails.guardrail_id > agent_guardrails.id [delete: cascade]
 Ref: agent_persona_traits.persona_id > agent_personas.id [delete: cascade]