[BUG] 'Filter' button text not translated on schedule page

[manjit1029]

Description

On the schedule page, the "Filter" button text is hardcoded and doesn't translate when switching between English and Spanish. The "Create Appointment" button translates correctly.

Steps to Reproduce

1. Log in as `admin@email.com` or `user-service@email.com`
2. Go to Schedule
3. Toggle language from EN to ES
4. "Filter" button text stays in English

Root Cause

`/pages/admin/scheduleView.vue`, line 31:
The button text is hardcoded as `Filter` instead of using `{{ $t("Filter") }}`.

Meanwhile, the FilterAppointments modal title (line 19) correctly uses `{{ $t("Filter Appointments") }}`.

i18n locale files (`/i18n/locales/`):

• `"Filter Appointments"` key exists but standalone `"Filter"` key may be missing from `es.json`

Fix

1. Change `Filter` to `{{ $t("Filter") }}` in scheduleView.vue line 31
2. Add `"Filter": "Filtrar"` to `/i18n/locales/es.json`
3. Add `"Filter": "Filter"` to `/i18n/locales/en.json`

Acceptance Criteria

• "Filter" button translates to "Filtrar" in Spanish
• Translation works on both admin and user-service schedule views