docs: update README and all docs with formal verification, new BaraQL features, OpenTelemetry tracing

- Add Formal Verification section to README and architecture docs
- Document TLA+ specs for Raft, 2PC, MVCC, Replication
- Add new BaraQL features: JSON path (->, ->>), FTS @@, CREATE INDEX USING FTS,
  RECOVER TO TIMESTAMP, UNION/INTERSECT/EXCEPT
- Add OpenTelemetry tracing example to README
- Update Quick Start to use nimble test/bench
- Update EN and BG documentation

docs/en/distributed.md

@@ -87,4 +87,24 @@ import barabadb/core/disttxn
 var dt = newDistributedTxn()
 dt.prepare(@["node1", "node2"])
 dt.commit()
+```
+
+## Formal Verification
+
+Core distributed algorithms are formally specified in TLA+ and model-checked:
+
+- **Raft Consensus** — `formal-verification/raft.tla`
+  - Verified: ElectionSafety, StateMachineSafety
+- **Two-Phase Commit** — `formal-verification/twopc.tla`
+  - Verified: Atomicity, NoOrphanBlocks
+- **Replication** — `formal-verification/replication.tla`
+  - Verified: MonotonicLsn, AcksRemovePending
+
+Run TLC locally:
+
+```bash
+cd formal-verification
+java -cp tla2tools.jar tlc2.TLC -config models/raft.cfg raft.tla
+java -cp tla2tools.jar tlc2.TLC -config models/twopc.cfg twopc.tla
+java -cp tla2tools.jar tlc2.TLC -config models/replication.cfg replication.tla
 ```