build(release): a Dart release tool for every app

tool/release.dart releases one app: `dart run tool/release.dart learn
[major | minor | patch] [--dry-run]`, each app configured in Dart beside
it (apps/learn/release.dart). Every step and check of tool/release.sh
is kept: the repository as pushed, resuming after a release commit and
tag, Flutter as CI pins it, the tools, the key and its certificate pin,
secrets asked for without echo and never written down, CI green on the
newest commit, the signed release commit and tag by a key deploys
accept, the APK built from a checkout of the tag and checked, the snap,
the signed checksums, pushing only after both builds passed, the
release on Forgejo, the F-Droid repository, the Snap Store once a
channel is set.

New: tags per app (learn-v0.19.0, Learn's v… counting as its
history); only commits touching the app decide its version (its folder,
the shared packages it uses by path, the root pubspec and lock, its
release files, where its packages were before the move); --dry-run
reads all of it, lists every step and the notes, and what a release
would refuse, changing nothing. The pure parts are tested in
test/release/. Learn releases build 21 with tool/release.sh, then
switches.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

pubspec.lock

@@ -355,7 +355,7 @@ packages:
     source: hosted
     version: "0.3.5+5"
   crypto:
-    dependency: transitive
+    dependency: "direct dev"
     description:
       name: crypto
       sha256: c8ea0233063ba03258fbcf2ca4d6dadfefe14f02fab57702265467a19f27fadf
@@ -913,7 +913,7 @@ packages:
     source: hosted
     version: "0.15.7"
   http:
-    dependency: transitive
+    dependency: "direct dev"
     description:
       name: http
       sha256: "87721a4a50b19c7f1d49001e51409bddc46303966ce89a65af4f4e6004896412"
@@ -1286,7 +1286,7 @@ packages:
     source: hosted
     version: "1.0.0"
   path:
-    dependency: transitive
+    dependency: "direct dev"
     description:
       name: path
       sha256: "75cca69d1490965be98c73ceaea117e8a04dd21217b37b292c9ddbec0d955bc5"
@@ -2381,7 +2381,7 @@ packages:
     source: hosted
     version: "7.0.1"
   yaml:
-    dependency: transitive
+    dependency: "direct dev"
     description:
       name: yaml
       sha256: f67cdd8e07d3c6329146aaef1ba043542b3134c12489f553ca9a7435d1068aea