feat(auth): install all authentication providers by default

All authentication methods (Basic Auth, Flask-Login, OAuth) are now
installed as core dependencies instead of optional extras. This
simplifies setup and eliminates the need to run `uv sync --extra auth-*`
when switching between authentication methods.

Changes:
- Move authlib, bcrypt, and flask-login to core dependencies
- Remove auth-* optional dependency groups from pyproject.toml
- Update documentation to remove installation instructions
- Simplify troubleshooting and migration guides

Benefits:
- No import errors when switching auth methods
- Simpler user experience
- All providers available out of the box

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

AUTHENTICATION.md

@@ -23,23 +23,7 @@ password = $2b$12$LQv3c1yqBWVHxkd0LHAkCOYz6TtxMQJqhN8/LewY5GyYWv.5qVQK6
 use_bcrypt = True
 ```
 
-### 2. Install Dependencies
-
-```bash
-# For Basic Auth
-uv sync --extra auth-basic
-
-# For Flask-Login
-uv sync --extra auth-login
-
-# For OAuth
-uv sync --extra auth-oauth
-
-# For all auth methods
-uv sync --extra auth-all
-```
-
-### 3. Restart TISBackup
+### 2. Restart TISBackup
 
 ```bash
 docker compose restart tisbackup_gui
@@ -332,12 +316,7 @@ docker logs tisbackup_gui | grep -i "auth"
 
 ### Basic Auth Not Working
 
-1. **Check bcrypt installation:**
-   ```bash
-   uv sync --extra auth-basic
-   ```
-
-2. **Verify password hash:**
+1. **Verify password hash:**
    ```bash
    python3 -c "import bcrypt; print(bcrypt.checkpw(b'yourpassword', b'$2b$12$your-hash'))"
    ```
@@ -354,12 +333,7 @@ docker logs tisbackup_gui | grep -i "auth"
    chmod 600 /etc/tis/users.txt
    ```
 
-2. **Module not found:**
-   ```bash
-   uv sync --extra auth-login
-   ```
-
-3. **Session problems:**
+2. **Session problems:**
    - Check `TISBACKUP_SECRET_KEY` is set
    - Ensure cookies are enabled
 
@@ -373,12 +347,7 @@ docker logs tisbackup_gui | grep -i "auth"
    - Verify email matches `authorized_users` or domain matches `authorized_domains`
    - Check OAuth provider returns email in user info
 
-3. **Module not found:**
-   ```bash
-   uv sync --extra auth-oauth
-   ```
-
-4. **Token errors:**
+3. **Token errors:**
    - Verify client ID and secret are correct
    - Check OAuth app is enabled
    - Ensure scopes are correct
@@ -415,17 +384,15 @@ Or implement API key authentication separately for API endpoints.
 ### From No Auth to Basic Auth
 
 1. Add authentication section to config
-2. Install bcrypt: `uv sync --extra auth-basic`
-3. Restart service
-4. Update client scripts with credentials
+2. Restart service
+3. Update client scripts with credentials
 
 ### From Basic Auth to OAuth
 
 1. Register OAuth application
 2. Update configuration
-3. Install dependencies: `uv sync --extra auth-oauth`
-4. Test OAuth login flow
-5. Update redirect URI if needed
+3. Test OAuth login flow
+4. Update redirect URI if needed
 
 ### From Flask-Login to OAuth