B.3: Add internal operational dashboard endpoint

[Copilot]

Implements the /admin/top-municipios monitoring endpoint that surfaces the most-searched municipalities by aggregating Micrometer counters — hidden from public Swagger and protected behind authentication.

Changes

• AdminDashboardController — New @Hidden @RestController at /admin/top-municipios; queries busca.municipio counters via Search.in(meterRegistry), returns top 10 sorted by search count descending ({municipio, uf, buscas})

• BuscaController — Injects MeterRegistry; increments busca.municipio{municipio, uf} counter on every /api/busca/perfil-direto call (the data source for the dashboard)

• SecurityConfig — Explicit .requestMatchers("/admin/**").authenticated() rule before the anyRequest catch-all

• application.yml — Sets management.server.port: 9090; adds metrics to actuator exposure

Example response

GET /admin/top-municipios

[
  { "municipio": "Campinas", "uf": "SP", "buscas": 42 },
  { "municipio": "Manaus",   "uf": "AM", "buscas": 17 }
]

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