MAJOR ARCHITECTURAL IMPROVEMENT:
Instead of using arbitrary timeouts that don't solve the real problem,
implement proper idle mode and explicit end-of-stream signaling.
Changes:
1. **Remove block_id timeout completely**
- No more BLOCK_ID_TIMEOUT_SECS
- Source enters idle mode when queue is empty
- Waits indefinitely for new block_ids (poll every 100ms)
- Only exits on cancellation or END_OF_BLOCKS_SIGNAL
2. **Introduce END_OF_BLOCKS_SIGNAL (EventId::MAX)**
- Special block_id value to signal "no more blocks"
- Source terminates cleanly after processing current block
- Allows proper shutdown without cancellation
- Exported from pmoparadise crate for public use
3. **Update HTTP timeout to 24 hours**
- Effectively infinite timeout for block downloads
- HTTP stream stays open as long as needed
- Closed by pipeline termination, not arbitrary timeout
4. **Update stream_block example**
- Push END_OF_BLOCKS_SIGNAL after the single block
- Demonstrates clean termination after one block
- Documents pattern for continuous vs. bounded streaming
Benefits:
- No arbitrary timeouts that might truncate valid streams
- Clean separation: cancellation (external) vs. completion (internal)
- Supports both continuous radio and bounded playlists
- Proper idle mode for on-demand streaming applications
Usage pattern:
```rust
// Single block then stop
source.push_block_id(block_id);
source.push_block_id(END_OF_BLOCKS_SIGNAL);
// Continuous streaming
source.push_block_id(block1);
source.push_block_id(block2);
// ... keep pushing or wait in idle mode
// Graceful shutdown
source.push_block_id(END_OF_BLOCKS_SIGNAL);
```