fix: Optimize IP detection logic and add error handling

[God-2077]

• The statistics for links and pixels on Vercel are not functioning correctly. #4038
• Check existence of clientIp and ignoreIps in advance
• Add error handling for CIDR parsing

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[greptile-apps]

Greptile Summary

This PR fixes a crash in the hasBlockedIp function in src/lib/detect.ts that occurred when clientIp was undefined or empty — a situation that arises on Vercel deployments where IP headers may not be present (issue #4038). The fix:

• Adds an early return when clientIp or ignoreIps is falsy, preventing ipaddr.parse(undefined) from throwing
• Removes a redundant inner if (ignoreIps) check that was already guarded by the outer condition
• Wraps CIDR parsing (ipaddr.parse / ipaddr.parseCIDR) in a try-catch to gracefully handle malformed IP addresses or CIDR ranges instead of crashing the entire /api/send route

Confidence Score: 4/5

• This PR is safe to merge — it adds defensive guards and error handling to an existing function without changing its core logic.
• The changes are small, well-scoped, and correct. The early return for falsy clientIp directly addresses the reported crash on Vercel. The try-catch around CIDR parsing prevents unhandled exceptions from malformed inputs. The only minor note is the use of .find() instead of .some(), which is a pre-existing style issue that doesn't affect correctness.
• No files require special attention.

Important Files Changed

Filename	Overview
src/lib/detect.ts	Refactors hasBlockedIp to add early return for missing clientIp/ignoreIps, removes redundant inner check, and wraps CIDR parsing in try-catch. Fixes a crash when clientIp is undefined (e.g., on Vercel). Minor style note: .find() should be .some() for boolean semantics.

Flowchart

flowchart TD
    A["hasBlockedIp(clientIp)"] --> B{clientIp and ignoreIps exist?}
    B -- No --> C[return false]
    B -- Yes --> D["Split ignoreIps by comma"]
    D --> E["For each ip in list"]
    E --> F{Exact match?}
    F -- Yes --> G[return true]
    F -- No --> H{CIDR notation?}
    H -- No --> I[return false]
    H -- Yes --> J["try: parse clientIp & CIDR range"]
    J --> K{Same kind & match?}
    K -- Yes --> G
    K -- No --> I
    J -- "catch: parse error" --> I

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