Size calibration speed vectors correctly

[BenJule]

Summary

Return correctly sized speed vectors for calibration setup.

Root cause

generate_max_speed_parameter_value() first resized the result vector to its final expected size and then appended the calculated values with emplace_back().

The returned vector therefore contained:

• a leading block of default-initialized zero values
• the calculated values appended after that block
• twice the expected number of entries

The function is used when preparing internal solid infill and top surface speed values for calibration.

Change

Reserve the expected capacity without changing the vector size before appending calculated values.

Validation

• verified both active Plater.cpp call sites
• verified the function contains reserve() and no result-vector resize()
• git diff --check
• targeted CalibUtils.cpp syntax check when a matching compile database entry is available
• one GPG-signed commit

No local full build was performed. Full application validation remains delegated to Jenkins.