refactor(datagen): thread an injected logger, drop global-logger use (PIPE-1067)

[Dylan-M]

Stacked on #276

Proposed Change

Removes global-logger (zap.L() / zap.S()) use so an embedding host has full
control over blitz's log stream.

• Threads an injected *zap.Logger through datagen's application generation,
  replacing the zap.L().Warn leak. A nil logger disables logging rather than
  falling back to the global.
• Adds a CI guard (scripts/check-no-global-logger.sh, wired into the Makefile and
  CI) that fails if zap.L() / zap.S() reappears outside bootstrap.

Validation: run the guard script against a tree with a deliberately-added zap.L()
call and confirm it fails. Tests thread the injected logger through and confirm
behavior with a nil logger.

Checklist

• Changes are tested
• CI has passed

[Dylan-M]

Warning

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• feat(config): reject invalid network CIDRs at environment load (PIPE-1002) #281
• feat(generators): emit simulated host identity on every record (PIPE-1036) #280
• feat(resource): support list-valued resource attributes (PIPE-1253) #279
• feat(datagen): environment foundations for simulated host identity (PIPE-1036) #278
• refactor(datagen): thread an injected logger, drop global-logger use (PIPE-1067) #277 👈 (View in Graphite)
• fix(datagen): return errors instead of panicking on developer-error input (PIPE-1003) #276
• feat(datagen): add IPv6 to NetworkIdentity and public emission (PIPE-1001) #275
• feat(datagen): add storage, network, and appliance-OS identities (PIPE-1035) #274
• main

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