Add ntfy authentication support (username/password and API key)

- Settings table gets ntfy_username, ntfy_password, ntfy_api_key columns
- Backend applies Basic or Bearer auth header when sending notifications
- Settings page UI lets you toggle between no auth, basic, or token auth
- Masked credential display on load to avoid exposing stored secrets
- README updated with auth modes documentation

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

README.md

@@ -12,7 +12,7 @@ Sproutly takes the guesswork out of seed starting. Enter your plant varieties on
 - **Seed Library** — manage plant varieties with frost-relative timing, germination days, sun/water requirements
 - **Garden Tracker** — log growing batches and track status from `planned` → `germinating` → `seedling` → `potted up` → `hardening off` → `garden` → `harvested`
 - **Year Timeline** — visual calendar showing when each variety's stages fall across the year
-- **Ntfy Notifications** — daily summary push notifications to your phone, configurable time and topic
+- **Ntfy Notifications** — daily summary push notifications to your phone, configurable time, topic, and authentication
 - **Settings** — set your last frost date, fall frost date, location, timezone, and notification preferences
 
 ## Stack
@@ -45,7 +45,7 @@ Access the app at **http://localhost:8053**
 ### First Steps
 
 1. Go to **Settings** and enter your last frost date — this anchors all planting schedule calculations
-2. Optionally configure an [ntfy](https://ntfy.sh) topic for push notifications
+2. Optionally configure an [ntfy](https://ntfy.sh) topic for push notifications — supports no auth, username/password, or API key/token
 3. Browse the pre-loaded **Seed Library** (12 common vegetables, herbs, and flowers included)
 4. Start logging batches in **My Garden** as you sow seeds
 
@@ -97,7 +97,18 @@ Key endpoints:
 - `GET/PUT /api/settings/` — app settings
 - `POST /api/notifications/test` — send test ntfy notification
 - `POST /api/notifications/daily` — trigger daily summary
+- `GET /api/notifications/log` — recent notification history
+
+## Ntfy Authentication
+
+For private ntfy servers or access-controlled topics, the Settings page supports three auth modes:
+
+| Mode | When to use |
+|------|-------------|
+| None | Public ntfy.sh topics |
+| Username & Password | ntfy server with basic auth enabled |
+| API Key / Token | ntfy account access token (generate in ntfy account settings) |
 
 ## Status
 
-This project is in early development. Core infrastructure and UI prototype are functional. UI design and feature set are evolving based on user feedback.
+Core infrastructure is functional. UI design and feature set are evolving based on user feedback.