refactor: extract global styles and tokens (Task 2.1)

- Create styles/tokens.css with CSS custom properties and dark theme
- Create styles/global.css with resets, shell layout, and navigation
- Create styles/utilities.css with generic utilities and primitives
- Create styles/syntax-highlight.css with Prism.js theme
- Update main.tsx to import the 4 new style files
- Keep styles.css intact for backward compatibility

Quality gates: build (pass), lint (pass)
Refs: repo-restructure Task 2.1

apps/api/src/schemas/project.py

@@ -0,0 +1,25 @@
+"""Project request/response schemas."""
+
+from pydantic import BaseModel
+
+
+class ProjectCreate(BaseModel):
+    name: str
+    description: str | None = None
+
+
+class ProjectUpdate(BaseModel):
+    name: str | None = None
+    description: str | None = None
+
+
+class ProjectResponse(BaseModel):
+    id: str
+    name: str
+    description: str | None
+    created_at: str
+    updated_at: str
+
+
+class SetDefaultSSHKeyRequest(BaseModel):
+    ssh_key_id: str