Add Visione backend foundation

docs/DATABASE_SCHEMA.md

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+# Visione Database Schema
+
+The schema is stored in `migrations/001_initial_schema.sql`.
+
+Important tables:
+
+- `users`: identity, personal data, password hash, points and moderation flags.
+- `roles`, `permissions`, `role_permissions`, `user_roles`: authorization.
+- `otp_challenges`: local OTP login flow.
+- `api_tokens`: bearer tokens for the local API.
+- `report_categories`: report classification.
+- `areas`: named city areas with GeoJSON polygon boundaries.
+- `team_categories`, `teams`: municipal intervention teams.
+- `reports`: citizen reports with coordinates, address, status and area.
+- `report_status_history`: immutable status transition log.
+- `assignments`: report-to-team assignment history.
+- `report_photos`: uploaded photo metadata.
+- `messages`: citizen/operator report conversation.
+- `feedback`: citizen rating and comment after resolution.
+- `reward_events`: indirect gamification points ledger.
+
+GeoJSON is intentionally used instead of MySQL Spatial in milestone 1 to keep
+the local setup simple and portable.
+