#21 — Rules tab: create and edit rule

[bobinush]

Rule properties:

• Name (required)
• Rule type: overlap (camp cannot overlap this area) or proximity (camp cannot be within X metres)
• Severity: low · medium · high
• Message: text shown to the user when the rule is violated
• Style override (optional): fill colour + opacity applied to the user's camp polygon when the rule fires

Acceptance criteria:

• All fields above are present in the form
• POST /api/rules on create; PUT /api/rules/:id on update
• The style override section is hidden behind a toggle and only submitted if enabled
• Cancel returns to the list without saving