Initial commit: Second Brain Platform

Complete platform with unified design system and real API integration.

Apps: Dashboard, Fitness, Budget, Inventory, Trips, Reader, Media, Settings
Infrastructure: SvelteKit + Python gateway + Docker Compose

docs/architecture.md

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+# Platform Architecture
+
+## Goal
+
+One frontend product with two sections:
+
+- `/trips`
+- `/fitness`
+
+Separate backend services remain in place:
+
+- `services/trips`
+- `services/fitness`
+
+The legacy frontends stay runnable during migration for fallback and comparison.
+
+## Service Boundaries
+
+- Trips backend remains independent.
+- Fitness backend remains independent.
+- Trips and Fitness keep separate SQLite databases.
+- Platform frontend owns the shared shell and explicit API proxy layer.
+
+## Proxy Contract
+
+- `/api/trips/*` -> Trips backend
+- `/api/fitness/*` -> Fitness backend
+
+Frontend code should call these proxy paths, not raw backend URLs.
+
+## Migration Order
+
+1. Keep both legacy frontends alive.
+2. Build platform shell.
+3. Add explicit proxy/API clients.
+4. Migrate one product area first.
+5. Migrate the second area.
+6. Retire legacy frontends only after full coverage.
+