Fix: Add missing forward declaration for deriveMacFromUid in Viewer sketch

[Copilot]

The Viewer sketch failed to compile because deriveMacFromUid() (defined at line 426) was called in setup() (line 246) with no prior forward declaration, causing an "undeclared in this scope" error.

Change

Added static void deriveMacFromUid(); to the existing forward declarations block alongside the other function prototypes:

// Before (missing entry):
static void scheduleNextSummaryFetch();

// After:
static void deriveMacFromUid();
static void scheduleNextSummaryFetch();

Original prompt

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This section details on the original issue you should resolve

<issue_title>Arduino Compilation Error in TankAlarm-112025-Viewer-BluesOpta (2026-03-13)</issue_title>
<issue_description>## Arduino Compilation Failed - TankAlarm 112025

The Arduino code compilation failed for the TankAlarm-112025 (Blues Opta) projects.

Workflow Run: https://github.com/SenaxInc/ArduinoSMSTankAlarm/actions/runs/23035782388
Commit: d9d19d6
Branch: master

Details

TankAlarm-112025 (Arduino Opta)

• Client Sketch: TankAlarm-112025-Client-BluesOpta/TankAlarm-112025-Client-BluesOpta.ino ✅
• Server Sketch: TankAlarm-112025-Server-BluesOpta/TankAlarm-112025-Server-BluesOpta.ino ✅
• Viewer Sketch: TankAlarm-112025-Viewer-BluesOpta/TankAlarm-112025-Viewer-BluesOpta.ino ❌

Board:

• Arduino Opta (arduino:mbed_opta:opta)

Triggered by: push

Next Steps

1. Review the workflow logs for detailed error messages
2. Fix compilation errors in the Arduino code
3. Re-run the workflow to verify the fix

/cc @copilot</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Arduino Compilation Error in TankAlarm-112025-Viewer-BluesOpta (2026-03-13) #280

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[Copilot]

Pull request overview

Fixes a Viewer sketch compile failure by adding a missing forward declaration so setup() can call deriveMacFromUid() before its definition later in the file.

Changes:

• Added static void deriveMacFromUid(); to the Viewer sketch’s forward-declarations block.

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