Add botan to Docker image

Dockerfile

@@ -22,6 +22,7 @@ ENV DEBIAN_FRONTEND=noninteractive \
 RUN apt-get update \
     && apt-get install -y --no-install-recommends \
         aria2 \
+        botan \
         ca-certificates \
         curl \
         ffmpeg \

README.md

@@ -30,7 +30,7 @@ Requirements:
 
 - `ani-cli` installed and available in `PATH`
 - Optional: `anipy-cli` installed and available in `PATH` if you want automatic fallback retries outside Docker
-- Common runtime tools used by `ani-cli`, especially `curl`, `ffmpeg`, `fzf`, `grep`, `openssl`, `sed`, `aria2c`, and `yt-dlp`
+- Common runtime tools used by `ani-cli`, especially `curl`, `ffmpeg`, `fzf`, `grep`, `openssl`, `sed`, `aria2c`, `botan`, and `yt-dlp`
 
 Run locally:
 
@@ -94,6 +94,7 @@ Docker notes:
 - `USER_UID` and `USER_GID` help keep mounted files owned by your host user
 - `UPDATE_ON_START=true` runs `ani-cli --update` before startup
 - `ANI_CLI_WEB_BRANCH` lets the image clone a specific `ani-cli-web` branch at build time
+- `botan` is installed inside the container for providers or scripts that need Botan cryptography tooling
 - `anipy-cli` is installed systemwide inside the container, so fallback retries are available without extra container setup
 
 ## Key behavior