Filewall: Secure Storage Provider

Filewall is a firewall for your files. It is a document provider built on Android's Storage Access Framework (SAF): files live in the app's own private storage, and every other app that wants to read, write or list them has to go through Filewall's rules.

How access is gated:
* The system's own SAF grant, as for any document provider.
* An optional PIN, with fingerprint or face unlock if you like. Turn it on in Settings.
* Your rules, evaluated top to bottom - the first match applies, like a firewall.

Key features:
* Rules per app, per folder or per file: allow read, write or list, block, or extend a rule to subfolders.
* Time-limited rules that expire on their own.
* When an app asks for something no rule covers, you get a request to allow or block it - one decision can answer a whole batch of requests.
* An optional access log that records what each app tried and why it was allowed or denied. It can be filtered and exported as CSV, and it can be switched off.
* No account, no analytics and no network access: Filewall does not declare the Internet permission. No root needed.

Permissions the app declares, and why:
* POST_NOTIFICATIONS - to tell you about access requests and blocked access (optional).
* USE_BIOMETRIC - fingerprint or face unlock in addition to the PIN (optional).
* RECEIVE_BOOT_COMPLETED - ends any open authentication session when the device restarts.
* QUERY_ALL_PACKAGES - lists your installed apps when you create a rule and shows the name and icon of the app asking for access. Nothing is stored or sent anywhere.

IMPORTANT: Filewall controls and restricts access; it does not encrypt your files. If you need encryption, combine it with an encryption tool. Threat model: it protects against unauthorized app access and accidental exposure on an unlocked device, not against root access or forensic tools.

Free software, GNU General Public License v3.

First public release.
* SAF document provider backed by the app's private storage.
* Per-app, per-folder and per-file rules, with time limits and block rules.
* App PIN with throttling, optional biometric unlock, screenshots blocked on protected screens.
* Access requests with batch decisions, and an optional filterable, exportable access log.