Errata fixes: batch 1 + batch 2 (12 issues resolved)

Opis

Serija ispravki grešaka u tehničkom sadržaju na srpskom jeziku, primenjena na fork-u acailic/toBeBetterJavaer grana fix/errata-batch-1.

Batch 1 (commit f68f72e) — 8 ispravki

Issue	Oblast	Ispravka
#201	JVM	Static variables on heap since JDK 7
#190	JUC	synchronized prevents cross-boundary reordering only
#185	Java SE	Float mantissa 25.125 = 1.1001001x2^4
#179	Network	SYN is 1-bit flag (SYN=2 -> SYN=1)
#191	Collections	HashMap uses equals() on hash collision
#142	Threads	join() blocks calling thread
#85	OS	7000+500=7500 (was 8700)
#187	Redis	repl-backlog vs replication buffer

Batch 2 (commit b7360d1) — 4 ispravke

Issue	Oblast	Ispravka
#196	MySQL	Undo log "snapshot" -> "old data before modification"
#195	Collections	ConcurrentHashMap iterator is weakly consistent
#131	String	Added thread safety as 4th reason for immutability
—	CDN	ai-agent.md migrated to cdn.paicoding.com

Napomene za maintainer

• PR-ovi #205, #204, #197, #200 ciljaju kineski tekst (vec preveden) — zatvoriti
• PR #186 uvodi typo javabebetter.cn — ne mergovati
• PR #194 semanticki pogresan — ne mergovati
• Issue #174 je spam — zatvoriti