Configurable slope values and colours

A new slope‑configuration panel where each activity type can have its own gradient logic. Instead of fixed brackets like the current versions, users should be able to build their own:

• Number of brackets
• Percentage boundaries
• Color per bracket
• Optional presets per activity (Hiking needs other values/number of brackets than cycling for example)

Why This Matters

• Different activities interpret slope differently.
• Hiking requires more granularity than cycling.
• Users regain the flexibility they previously had, but with a cleaner UI.