feat: Add API key authentication for backup tool

- Add get_api_key() and require_api_key() to auth.py
- Add generic key-value settings storage to SettingsStore
- Add test_api_key_auth to verify the implementation
- Uses secrets.compare_digest for timing-safe comparison
- Auto-generates API key on first use and stores in settings DB

docs/superpowers/specs/2026-05-08-obsidian-documentation-design.md

@@ -0,0 +1,53 @@
+# Obsidian Documentation Structure for Manage (Media Library Viewer)
+
+**Date:** 2026-05-08
+**Status:** Approved
+
+## Purpose
+
+Create a comprehensive, interconnected Obsidian documentation vault for the Manage project (media library viewer application). The documentation targets all audiences: future developers, contributors, operators, and deployers.
+
+## Structure
+
+### Map of Content (MOC)
+- `manage/Overview.md` — Central hub with wikilinks to all documentation areas
+
+### Architecture & Overview
+- `manage/Architecture.md` — System design, data flow, tech stack
+- `manage/Directory Structure.md` — Annotated codebase layout
+
+### Backend
+- `manage/Backend/API Endpoints.md` — Complete REST endpoint map
+- `manage/Backend/Configuration.md` — Settings, env vars, OIDC
+- `manage/Backend/Services.md` — Core services: settings store, media index, poller, mail
+- `manage/Backend/Clients.md` — External integrations: Jellyfin, Jellyseerr, SSH
+
+### Frontend
+- `manage/Frontend/Pages & Routing.md` — Routes, page components
+- `manage/Frontend/Components.md` — Reusable components
+- `manage/Frontend/State & Data.md` — Hooks, QueryClient, data fetching
+- `manage/Frontend/Auth & Theme.md` — OIDC auth, MUI theme
+
+### Deployment
+- `manage/Deployment/Production.md` — Docker Compose, Traefik, TLS
+- `manage/Deployment/Development.md` — Dev workflow, hot reload
+
+### Operations
+- `manage/Operations/Machine Management.md` — SSH keys, collectors
+- `manage/Operations/Monitoring.md` — Poller, metrics
+- `manage/Operations/Tasks & Jobs.md` — Saved tasks, job templates
+
+### Development
+- `manage/Development/Setup.md` — Getting started for backend + frontend
+- `manage/Development/Testing.md` — Test structure and commands
+- `manage/Development/Contributing.md` — Conventions, PR workflow
+
+## Cross-Linking Conventions
+- Every note uses YAML frontmatter with `tags` and `aliases`
+- Related docs linked via `[[wikilinks]]`
+- Callouts for warnings, tips, and notes
+
+## Technologies Referenced
+- Backend: Python 3.11+, FastAPI, SQLite, Paramiko, PyJWT
+- Frontend: React 19, TypeScript 6, Vite 8, MUI 9, D3 7, AG Grid
+- Infra: Docker, Traefik, Authentik/OIDC