feat: add archiving of platform media files (#1)

* chore: specify non-ignored `.md` files

* refactor: rename youtube downloader to ytdlp

More generic name since yt-dlp supports many sites beyond YouTube.

* feat: add local file downloader

Supports file:// URLs for archiving local files.

* deps: add regex crate for URL pattern matching

* feat: expand source detection with granular YouTube types

- Split Source::YouTube into YouTubeVideo, YouTubePlaylist, YouTubeChannel
- Add Source::X for Twitter/X posts
- Add Source::Local for file:// URLs
- Add regex-based URL pattern matching for YouTube URLs
- Add shorthand schemes (yt:video/ID, youtube:playlist/ID, etc.)
- Add comprehensive tests for all URL patterns

* docs: update README milestones

Mark YouTube videos, Twitter videos, and local files as done.

* chore: update flake.lock

* feat: add shorthand schemes for X/Twitter media

* chore: move docs into docs dir

* Remove temp file using timestamp path

Delete the temp entry at store_path/temp/<timestamp> in both
the hash-exists and success paths. Stop constructing the full filename
with extension and remove the early process::exit to de-duplicate
cleanup.

* Add Nix caches and default flake package

* Add social platform source detection and update milestones

* Tighten social URL matching to avoid false positives

* Mark media archiving milestone complete

flake.nix

@@ -1,6 +1,18 @@
 {
   description = "Archivr - An open-source archive manager";
 
+  nixConfig = {
+    extra-substituters = [
+      "https://cache.thegeneralist01.com/"
+      "https://cache.garnix.io/"
+      "https://cache.nixos.org/"
+    ];
+    extra-trusted-public-keys = [
+      "cache.thegeneralist01.com:jkKcenR877r7fQuWq6cr0JKv2piqBWmYLAYsYsSJnT4="
+      "cache.garnix.io:CTFPyKSLcx5RMJKfLo5EEPUObbA78b0YQ2DTCJXqr9g="
+    ];
+  };
+
   inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
 
   outputs =
@@ -21,7 +33,7 @@
             pname = "archivr";
             version = "0.1.0";
             src = pkgs.lib.cleanSource ./.;
-            cargoHash = "sha256-y47+Fmp3BID86aPnLtrvzg40lOr9cHyg/38+onisK7w=";
+            cargoHash = "sha256-4m+4SMYA/rJ0eHEOc32zA2VdZI1pqzB5NenD0R0f2zM=";
             nativeBuildInputs = [ pkgs.pkg-config ];
           };
           archivr = pkgs.stdenv.mkDerivation {
@@ -49,6 +61,7 @@
           };
         in
         {
+          default = archivr;
           archivr = archivr;
           archivr-unwrapped = archivr_unwrapped;
         }