Add authentication to File Manager and Adminer views

[twinvega]

The File Manager and Adminer views in views.php had no ensure_authenticated()
call, unlike every other privileged view (System Controls, Services, Webterm,
Species Management, etc.).

This means anyone who sets CADDY_PWD in birdnet.conf directly — a workaround
documented in multiple community issues [1][2] — ends up with PHP auth
enforced but Caddy's basicauth unchanged. The file manager at
/scripts/filemanager/filemanager.php remains accessible without credentials,
exposing birdnet.conf (including the plaintext CADDY_PWD) to unauthenticated
users.

Fix: add ensure_authenticated() before the File and Adminer includes,
consistent with how Webterm is already handled.

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Password Change Does Not Protect the File Manager

When a user sets a password by editing /etc/birdnet/birdnet.conf directly —
a documented community workaround recommended in multiple GitHub issues [1][2]
— update_caddyfile.sh is never called. CADDY_PWD is set, PHP requires the
password, but Caddy has no auth configured. The user confirms the login prompt
is working and believes the instance is secured. The file manager remains wide
open.

How it plays out

1. User sets CADDY_PWD=hunter2 in /etc/birdnet/birdnet.conf
2. PHP's auth starts requiring the password — user confirms it's working
3. Caddy's auth is never updated — either because update_caddyfile.sh was never run, or because it failed silently when called from the web interface (caddy is not in PHP's PATH, leaving HASHWORD empty and the generated Caddyfile malformed) — file manager remains accessible
4. Attacker recovers the plaintext password directly from birdnet.conf:

HOST="http://target"
USER=$(curl -s "$HOST/scripts/filemanager/filemanager.php?p=" \
  | grep -oE 'p=[a-z][a-z0-9_-]+' | head -1 | cut -d= -f2)
curl -s "$HOST/scripts/filemanager/filemanager.php?p=${USER}%2FBirdNET-Pi&dl=birdnet.conf" \
  | grep "CADDY_PWD"

CADDY_PWD=hunter2

5. Attacker uses the recovered password against authenticated RCE endpoints

[1] mcguirepr89#889
[2] mcguirepr89#749