feat(core,stream,meta,app,android,cli): sign in to Proton and sync watch history

A Proton account is now optional alongside public links. Signing in (password,
then a second-factor code and a mailbox password where the account has them;
a CAPTCHA gate is solved in the Android app) stores one session blob in the OS
credential store under `proton-account`, writing back every refreshed token
since refresh tokens are single-use. With an account, folders of the viewer's
own Drive — My Files, other devices, shared with me — can be added as shares
through the same `ShareClient` surface as a public link.

Watch history syncs through a `proton-stream` device in that Drive: one
`watch-history/<installation>.json` per installation, so no two devices ever
write the same file. Each sync reads the others and merges per episode, newer
`updated_at` wins, with a deterministic tie-break. It runs at launch, after
sign-in, whenever the player closes and every five minutes. A session that can
no longer refresh signs the app out instead of failing on every launch.

The CLI gains `login`, `logout`, `account`, `browse` and `sync`.

Also in this change:
- Android offline downloads no longer look stuck (B64): two transfer at once,
  through a copy stream with no read-ahead, with a smoothed transfer rate.
- Choosing a metadata match by hand now enriches the title too, instead of
  keeping the old match's episodes and artwork.

The catalog schema is unchanged.

crates/pstr-stream/src/lib.rs

@@ -42,4 +42,4 @@ pub use proton_sdk::ids::NodeUid;
 pub use reader::{FileBlocks, LibraryOpener, RevisionBlocks};
 pub use ring::{DEFAULT_RING_BYTES, RingStats};
 pub use source::{RevisionOpener, StreamConfig, StreamSource};
-pub use stream::{DEFAULT_READAHEAD_BLOCKS, StreamStats, VideoStream};
+pub use stream::{COPY_BLOCKS_IN_FLIGHT, DEFAULT_READAHEAD_BLOCKS, StreamStats, VideoStream};

crates/pstr-stream/src/reader.rs

@@ -13,7 +13,6 @@ use std::sync::Arc;
 use std::time::Duration;
 
 use async_trait::async_trait;
-use proton_drive_rs::ProtonDrivePublicLinkClient;
 use proton_sdk::error::ProtonError;
 use proton_sdk::ids::NodeUid;
 
@@ -159,7 +158,7 @@ impl LibraryOpener {
         Self { library }
     }
 
-    fn client(&self, share_id: &str) -> Result<&ProtonDrivePublicLinkClient> {
+    fn client(&self, share_id: &str) -> Result<&pstr_core::ShareClient> {
         self.library
             .client(share_id)
             .ok_or_else(|| Error::NotFound(format!("share {share_id} is not open")))

crates/pstr-stream/src/stream.rs

@@ -63,6 +63,12 @@ const MAX_CONCURRENT_BLOCKS_PER_READ: usize = 4;
 /// bandwidth on cancelled prefetches. Well past a 1080p bitrate either way.
 pub const DEFAULT_READAHEAD_BLOCKS: usize = 12;
 
+/// How many blocks of one offline copy are fetched at once, for
+/// [`VideoStream::blocks_in_order`]. The same as one read is allowed, for the
+/// same reason: enough to hide a round trip, few enough that a couple of
+/// copies running together do not swamp a player.
+pub const COPY_BLOCKS_IN_FLIGHT: usize = 4;
+
 /// How far a read may land from where the previous one ended and still count as
 /// a continuation rather than a seek.
 ///
@@ -299,6 +305,42 @@ impl VideoStream {
         Ok(buf)
     }
 
+    /// Every block from `first` on, fetched `in_flight` at a time and yielded
+    /// in file order.
+    ///
+    /// What an offline copy reads through. File order is what a partial file's
+    /// "its length is a block boundary" resume rule needs, and a few blocks in
+    /// flight is what keeps a copy from running one round trip per block. Use
+    /// it on a stream from [`crate::StreamSource::open_for_copy`]: a playback
+    /// stream would add its own read-ahead on top.
+    pub fn blocks_in_order(
+        &self,
+        first: usize,
+        in_flight: usize,
+    ) -> futures::stream::BoxStream<'static, Result<Vec<u8>>> {
+        let start: u64 = self.block_sizes()[..first.min(self.block_sizes().len())]
+            .iter()
+            .sum();
+        let ranges: Vec<(u64, u64)> = self
+            .block_sizes()
+            .iter()
+            .skip(first)
+            .scan(start, |offset, size| {
+                let range = (*offset, *size);
+                *offset += size;
+                Some(range)
+            })
+            .collect();
+        let stream = self.clone();
+        stream::iter(ranges)
+            .map(move |(offset, size)| {
+                let stream = stream.clone();
+                async move { stream.read_range(offset, size).await }
+            })
+            .buffered(in_flight.max(1))
+            .boxed()
+    }
+
     pub fn stats(&self) -> StreamStats {
         StreamStats {
             ring: self.inner.ring.stats(),