chore: Migrate redigo to go-redis, upgrade throttled

[mschfh]

Summary

This PR replaces our outdated redigo dependency with go-redis.

Type of Change

• Product feature
• Bug fix
• Performance improvement
• Refactor
• Other

Tested Environments

• Development
• Staging
• Production

Before Requesting Review

• Does your code build cleanly without any errors or warnings?
• Have you used auto closing keywords?
• Have you added tests for new functionality?
• Have validated query efficiency for new database queries?
• Have documented new functionality in README or in comments?
• Have you squashed all intermediate commits?
• Is there a clear title that explains what the PR does?
• Have you used intuitive function, variable and other naming?
• Have you requested security and/or privacy review if needed
• Have you performed a self review of this PR?

[clD11]

LGTM approved with comments.

[github-actions]

[puLL-Merge] - brave-intl/bat-go@2737

Description

This PR updates Redis and rate limiter dependencies to newer versions and improves Docker build caching. The main changes involve:

1. Migrating from the legacy gomodule/redigo Redis client to the modern redis/go-redis/v9
2. Upgrading the rate limiter from throttled to throttled/v2
3. Adding Docker build cache for go mod downloads

Changes

Changes

Dockerfile

• Added build cache for go mod downloads using --mount=type=cache
• Standardized stage naming convention to uppercase AS

Redis Client Changes

• Changed Redis client from gomodule/redigo to redis/go-redis/v9 across multiple packages
• Updated all Redis operations to use new client APIs and context support
• Removed manual connection management code as go-redis handles pooling internally

Rate Limiter Changes

• Updated from throttled to throttled/v2 package
• Migrated to newer context-aware APIs (GCRAStoreCtx, HTTPRateLimiterCtx, etc.)
• Updated rate limiter middleware to use new APIs

Dependency Updates

• Added various new Redis deps like dgryski/go-rendezvous
• Updated go.mod and go.sum files across multiple packages
• Removed old Redis and rate limiter dependencies

sequenceDiagram
    participant App
    participant RateLimiter
    participant Redis
    
    App->>RateLimiter: HTTP Request
    RateLimiter->>Redis: Check Rate Limit (with context)
    Redis-->>RateLimiter: Return Current Count
    alt Under Limit
        RateLimiter->>App: Allow Request
    else Over Limit
        RateLimiter->>App: Return 429 Too Many Requests
    end

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Security Hotspots

• Redis security considerations have not materially changed as connection security is handled through connection strings/URLs
• Rate limiting security remains consistent but now has proper context support for cancellation