docs: restructure docs into diataxis (#121)

docs/how-to/file-transfer.md

@@ -0,0 +1,59 @@
+# File transfer
+
+Upload files into the active repo/worktree or fetch files back into Telegram.
+
+## Enable file transfer
+
+```toml
+[transports.telegram.files]
+enabled = true
+auto_put = true
+auto_put_mode = "upload" # upload | prompt
+uploads_dir = "incoming"
+allowed_user_ids = [123456789]
+deny_globs = [".git/**", ".env", ".envrc", "**/*.pem", "**/.ssh/**"]
+```
+
+Notes:
+
+- File transfer is **disabled by default**.
+- If `allowed_user_ids` is empty, private chats are allowed and group usage requires admin privileges.
+
+## Upload a file (`/file put`)
+
+Send a document with a caption:
+
+```
+/file put <path>
+```
+
+Examples:
+
+```
+/file put docs/spec.pdf
+/file put /happy-gadgets @feat/camera assets/logo.png
+```
+
+If you send a file **without a caption**, Takopi saves it to `incoming/<original_filename>`.
+
+Use `--force` to overwrite:
+
+```
+/file put --force docs/spec.pdf
+```
+
+## Fetch a file (`/file get`)
+
+Send:
+
+```
+/file get <path>
+```
+
+Directories are zipped automatically.
+
+## Related
+
+- [Commands & directives](../reference/commands-and-directives.md)
+- [Config reference](../reference/config.md)
+