Allow medications with only a generic name (no commercial name required) (#311)

* Initial plan

* feat: allow generic name only for medications (frontend changes)

- Add getMedDisplayName() helper for consistent name display
- Update validation to require either commercial or generic name
- Update all display locations to use display name fallback
- Add i18n keys for nameOrGenericRequired in en.json and de.json
- Remove required attribute from commercial name field
- Update FIELD_LIMITS.name.min from 1 to 0

Co-authored-by: DanielVolz <3275994+DanielVolz@users.noreply.github.com>

* feat: allow generic name only for medications (backend changes)

- Update Zod schema to allow empty name with cross-field refinement
- Update reminder scheduler to use name || genericName for display
- Update planner routes to match medications by display name
- Update existing tests to match new validation behavior

Co-authored-by: DanielVolz <3275994+DanielVolz@users.noreply.github.com>

* fix: update placeholder text and fix FIELD_LIMITS test

- Remove "(optional)" from generic name placeholder in en/de
- Update types.test.ts to expect FIELD_LIMITS.name.min = 0

Co-authored-by: DanielVolz <3275994+DanielVolz@users.noreply.github.com>

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: DanielVolz <3275994+DanielVolz@users.noreply.github.com>

frontend/src/pages/PlannerPage.tsx

@@ -5,6 +5,7 @@ import { DateTimeInput, MedicationAvatar } from "../components";
 import { useAuth } from "../components/Auth";
 import { useAppContext } from "../context";
 import type { PlannerRow } from "../types";
+import { getMedDisplayName } from "../types";
 import { toInputValue } from "../utils/formatters";
 
 // Date helpers
@@ -204,7 +205,7 @@ export function PlannerPage() {
 							</div>
 							{plannerRows.map((row) => {
 								const med =
-									meds.find((m) => m.id === row.medicationId) || meds.find((m) => m.name === row.medicationName);
+									meds.find((m) => m.id === row.medicationId) || meds.find((m) => getMedDisplayName(m) === row.medicationName);
 								const remainingRefills = med?.prescriptionEnabled ? (med.prescriptionRemainingRefills ?? 0) : null;
 								return (
 									<div