#281 configurable max-cycles via MAX_CYCLES env var

[VasilevNStas]

baza.rb currently has no way to control the max cycle count without modifying entry.sh.

Makes --max-cycles configurable via MAX_CYCLES environment variable. Falls back to 3 (current default):

./entry.sh job123 /tmp        # 3 cycles
MAX_CYCLES=10 ./entry.sh job123 /tmp  # 10 cycles

@yegor256 please review

[VasilevNStas]

Why this matters

max-cycles=3 is hardcoded. This works for most judges, but some need more cycles to converge (e.g. gradual consensus-building judges) and some would benefit from fewer (e.g. expensive AI judges where you want to fail fast).

Before this PR, changing the cycle count requires forking entry.sh or patching the Docker image — both maintenance nightmares.

After this PR, baza.rb simply sets MAX_CYCLES=10 per job and the same entry.sh handles it. No forks, no patches, no image rebuilds.