test: add full test coverage for notes, ues, ue-modules, ajustements, enseignements, users

- Unit tests (mock DB + API) for all missing endpoints
- Integration tests (Drizzle direct) for all missing entities
- E2E tests (handler + real DB) for all missing endpoints
- Robustness tests: invalid inputs, SQL injection, type errors, business rule violations
- Seed helpers: seedNotes, seedUeModules, seedEnseignements, seedAjustements
- Add test:coverage and test:coverage:html tasks to deno.json

Tests expose known handler bugs (marked [BUG] in test names):
- ajustements PUT/DELETE: .where() without and() modifies all rows for student
- Missing try/catch in modules, users, enseignements handlers
- Whitespace accepted as valid string values
- No type or business rule validation (note bounds, coeff >= 0)

tests/helpers/db_integration.ts

@@ -87,3 +87,27 @@ export async function seedUsers(
 ): Promise<typeof schema.users.$inferSelect[]> {
   return await testDb.insert(schema.users).values(rows).returning();
 }
+
+export async function seedNotes(
+  rows: { numEtud: number; idModule: string; note: number }[],
+): Promise<typeof schema.notes.$inferSelect[]> {
+  return await testDb.insert(schema.notes).values(rows).returning();
+}
+
+export async function seedUeModules(
+  rows: { idModule: string; idUE: number; idPromo: string; coeff: number }[],
+): Promise<typeof schema.ueModules.$inferSelect[]> {
+  return await testDb.insert(schema.ueModules).values(rows).returning();
+}
+
+export async function seedEnseignements(
+  rows: { idProf: string; idModule: string; idPromo: string }[],
+): Promise<typeof schema.enseignements.$inferSelect[]> {
+  return await testDb.insert(schema.enseignements).values(rows).returning();
+}
+
+export async function seedAjustements(
+  rows: { numEtud: number; idUE: number; valeur: number }[],
+): Promise<typeof schema.ajustements.$inferSelect[]> {
+  return await testDb.insert(schema.ajustements).values(rows).returning();
+}