feat(bluesky): add bluesky_jetstream input for AT Protocol firehose

[aronchick]

Summary

• Add new bluesky_jetstream input component for streaming AT Protocol events
• Connects to Bluesky Jetstream WebSocket service for real-time firehose data
• Supports filtering by collections and DIDs, zstd compression, cursor-based resumption

Features

• WebSocket-based streaming from Jetstream public endpoints
• Support for custom PDS endpoints
• Collection and DID filtering (up to 100 collections, 10,000 DIDs)
• zstd compression support for reduced bandwidth
• Cursor-based resumption via cache resource
• Automatic endpoint failover
• Configurable ping/pong keepalive

Event Types

• commit: Repository changes (posts, likes, follows, blocks, etc.)
• identity: Handle and identity changes
• account: Account status changes

Test plan

• Unit tests pass locally (9 tests)
• Build succeeds
• CI validation

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