feat: implement search terms worksheet functionality

[kallilsouza]

What

Adds a new SEARCH_TERMS section to the Conversations Report generation flow. When this section is selected, the generated report includes an extra "Search terms" worksheet containing the contact URN, the event date, and the searched term, sourced from datalake weni_nexus_data events filtered by a configurable agent UUID and key.

Changes include:

• New SEARCH_TERMS value in ConversationsReportSections.
• New abstract method get_search_terms_worksheet on BaseConversationsReportService and its concrete implementation on ConversationsReportService.
• SEARCH_TERMS registered in the worksheet mapping (_get_worksheets) and in the available widgets/sections list.
• Settings-driven configuration via CONVERSATIONS_METRICS_SEARCH_TERMS_AGENT_UUID and CONVERSATIONS_METRICS_SEARCH_TERMS_KEY, raising SearchTermsAgentUUIDNotConfiguredError when the agent UUID is missing.
• PT-BR and ES translations for the new "Search terms" and "Terms" strings.
• Unit tests covering: successful worksheet generation, empty-data fallback row, missing-agent-UUID error path, and worksheet dispatch through _get_worksheets.

Why

Customers need visibility into the search terms used by end contacts so they can analyze data directly from the Conversations Report. Exposing this data as an additional worksheet inside the existing report keeps the flow consistent with the other sections (CSAT, NPS, Tool Results, etc.) and reuses the datalake integration already in place.

Sequence diagram

sequenceDiagram
    participant Client
    participant View as ReportsView
    participant Serializer as RequestConversationsReportGenerationSerializer
    participant Service as ConversationsReportService
    participant Settings as Django settings
    participant Datalake as Datalake events
    participant Worksheet as ConversationsReportWorksheet

    Client->>View: POST generate report (sections=[SEARCH_TERMS])
    View->>Serializer: validate payload
    Serializer-->>View: validated data
    View->>Service: generate report
    Service->>Service: _get_worksheets(report, start_date, end_date)
    Service->>Service: dispatch SEARCH_TERMS -> get_search_terms_worksheet
    Service->>Settings: read CONVERSATIONS_METRICS_SEARCH_TERMS_AGENT_UUID
    alt agent_uuid is empty
        Settings-->>Service: ""
        Service-->>View: raise SearchTermsAgentUUIDNotConfiguredError
    else agent_uuid is configured
        Settings-->>Service: agent_uuid
        Service->>Settings: read CONVERSATIONS_METRICS_SEARCH_TERMS_KEY
        Settings-->>Service: search_term_key
        Service->>Datalake: get_datalake_events(event_name=weni_nexus_data, key, metadata_key=agent_uuid, metadata_value)
        Datalake-->>Service: events list
        Service->>Service: translate headers using requester language
        alt events list is empty
            Service->>Worksheet: build worksheet with empty row
        else events list has items
            Service->>Worksheet: build rows (URN, Date, Terms)
        end
        Worksheet-->>Service: ConversationsReportWorksheet
        Service-->>View: worksheets including Search terms
        View-->>Client: report generated
    end

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