docs: add boot sequence documentation for v2.0 deployment
Add comprehensive boot-sequence.md covering: - Service components (core and monitoring) with lifecycle types - Startup order flowchart with dependency signals - Sync stages state machine (SYNCING → APPLYING_INDEXES → LIVE) - Health check methods for all services - Shared resources with volume paths per network (mainnet/preprod) The new index-applier service introduced in v2.0 is documented, including the deferred index creation strategy that reduces initial sync time by ~6 hours on mainnet. Also fixes: - Reorder sidebar positions to place boot-sequence first - Add missing Tabs component import in hardware-profiles.md