docs(project): add planning diagrams and report deliverables

docs/architecture-diagram.md

@@ -0,0 +1,48 @@
+# SecureCam codebase architecture
+
+```mermaid
+flowchart LR
+  CAMERA["Camera device
+  Mobile camera app / browser simulator"]:::client
+
+  USER["User devices
+  Web app / mobile app"]:::client
+
+  subgraph PLATFORM["SecureCam platform"]
+    BACKEND["Backend service
+    • authentication
+    • device coordination
+    • live stream control
+    • motion events
+    • recordings access"]:::backend
+  end
+
+  DATA["Core data layer
+  PostgreSQL"]:::data
+
+  MEDIA["Media storage
+  MinIO / S3-compatible object storage"]:::data
+
+  NOTIFY["Notifications
+  push + in-app activity updates"]:::service
+
+  CAMERA -->|"motion, stream, recordings"| BACKEND
+  USER -->|"auth, viewing, control"| BACKEND
+
+  BACKEND -->|"app state, users, devices, events"| DATA
+  BACKEND -->|"video and recording assets"| MEDIA
+  BACKEND -->|"alerts and activity fan-out"| NOTIFY
+
+  NOTIFY --> USER
+
+  classDef client fill:#e8f1ff,stroke:#3b82f6,stroke-width:2px,color:#111827;
+  classDef backend fill:#ecfdf3,stroke:#16a34a,stroke-width:2px,color:#111827;
+  classDef data fill:#fff7e8,stroke:#f59e0b,stroke-width:2px,color:#111827;
+  classDef service fill:#f3e8ff,stroke:#9333ea,stroke-width:2px,color:#111827;
+```
+
+## Notes
+
+- This version is intentionally high level.
+- It treats the web app, mobile app, and simulator as client surfaces around one backend platform.
+- Internal backend modules such as routes, workers, realtime gateway, and media scaffolding are abstracted into a single service block.