fix: use plain fetch instead of this.fetch in analytics methods

[giladresisi]

Problem

this.fetch (from SocialAbstract) is the posting wrapper: it routes response bodies through handleErrors(), sleeps 5s and retries on 429/500, and throws Temporal ApplicationFailures (BadBody/RefreshToken). None of that belongs in analytics calls served from the backend API — and it forces analytics concerns into handleErrors, as seen in #1665 (review: "this.fetch should not be connected with pinterest analytics").

Changes

Swapped this.fetch → plain fetch (the pattern every existing analytics() implementation already uses) in every analytics method that used it:

• Pinterest — postAnalytics
• Facebook — postAnalytics
• Instagram — postAnalytics
• LinkedIn Page — postAnalytics (2 calls)
• Threads — postAnalytics
• TikTok — analytics (3 calls) and postAnalytics (2 calls)

On failure these methods now fall into their existing catch/fallback paths and return empty data, same as the plain-fetch analytics methods behave today. Non-analytics uses of this.fetch (posting, TikTok missing(), LinkedIn repost plug) are untouched.

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[postiz-contribution]

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