Add notes API: clinic + author-scoped CRUD

New `note` table (src/db/schema/notes.ts) referencing organization + user,
with org+author scoping so a doctor only sees their own notes within the active
clinic. Adds:

- src/types/note.ts + src/lib/note-validation.ts (zod)
- src/services/notes.ts (CRUD, treats non-uuid ids as not-found)
- src/routes/notes.ts mounted at /api/notes, gated requireAuth → requireOrg
- schema barrel + generated migration drizzle/0001_*.sql (applied on startup
  by the runtime migrator)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/src/types/note.ts

@@ -0,0 +1,9 @@
+// The canonical Note shape returned by the API. Mirrors the frontend
+// `lib/notes.ts` Note type. `content` is rich-text editor HTML.
+export type Note = {
+  id: string;
+  title: string;
+  content: string;
+  createdAt: string;
+  updatedAt: string;
+};