Refactor duplicated code patterns

[Copilot]

Eliminates code duplication across bot commands, competition handlers, and validation utilities.

Changes

• Date update handlers: Consolidated handleUpdateStartDate and handleUpdateEndDate (~50 duplicate lines) into parameterized updateCompetitionDate helper

• Type assertions: Extracted repeated assertion patterns into assertUserInfo and assertUserAdditionalInfo helpers (3 instances)

• String normalization: Created normalizeString helper for strings.ToLower(strings.TrimSpace()) pattern (4 call sites)

• Pattern matching: Unified ContainsSQLInjection and ContainsDiscordAbuse (~20 duplicate lines) via generic containsPatterns function

Example

Before:

func handleUpdateStartDate(s *discordgo.Session, m *discordgo.MessageCreate, dateStr string, competition *models.Competition) {
    errorHandlers := utils.NewErrorHandlerFactory(s, m.ChannelID)
    startDate, err := utils.ParseDateWithValidation(dateStr, "start")
    if err != nil { errorHandlers.Validation().HandleInvalidDateFormat("START"); return }
    if !utils.IsValidDateRange(startDate, competition.EndDate) { 
        errorHandlers.Validation().HandleInvalidDateRange(); return 
    }
    err = ch.commandHandler.deps.Storage.UpdateCompetitionStartDate(startDate)
    // ... error handling and success message
}

func handleUpdateEndDate(/* same logic with end date */) { }

After:

func handleUpdateStartDate(s *discordgo.Session, m *discordgo.MessageCreate, dateStr string, competition *models.Competition) {
    ch.updateCompetitionDate(s, m, dateStr, competition, true)
}

func handleUpdateEndDate(s *discordgo.Session, m *discordgo.MessageCreate, dateStr string, competition *models.Competition) {
    ch.updateCompetitionDate(s, m, dateStr, competition, false)
}

func updateCompetitionDate(s *discordgo.Session, m *discordgo.MessageCreate, dateStr string, competition *models.Competition, isStartDate bool) {
    // Single implementation handles both cases via parameterization
}

Original prompt

Find and refactor duplicated code

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