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/lib/note-validation.ts

@@ -0,0 +1,10 @@
+import { z } from "zod";
+
+// Payload accepted by POST/PUT /api/notes. `content` is editor HTML (capped to
+// avoid unbounded payloads).
+export const noteInputSchema = z.object({
+  title: z.string().trim().min(1, "Title is required.").max(200),
+  content: z.string().max(100_000).default(""),
+});
+
+export type NoteInput = z.infer<typeof noteInputSchema>;