feat(server): implement full REST API with JWT auth and real-time WebSocket

- Add HTTP handlers for issues, comments, agents, workspaces, inbox, members, and activity
- Implement JWT authentication middleware with Bearer token validation
- Add sqlc queries for all entities (CRUD operations)
- Extract router into reusable NewRouter() for testability
- Expand SDK with full API client methods (CRUD for all resources)
- Add updateWorkspace to SDK, add Member type to shared types

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/pkg/db/queries/activity.sql

@@ -0,0 +1,11 @@
+-- name: ListActivities :many
+SELECT * FROM activity_log
+WHERE issue_id = $1
+ORDER BY created_at DESC
+LIMIT $2 OFFSET $3;
+
+-- name: CreateActivity :one
+INSERT INTO activity_log (
+    workspace_id, issue_id, actor_type, actor_id, action, details
+) VALUES ($1, $2, $3, $4, $5, $6)
+RETURNING *;