Fix a whole slew of problems

[davidnewhall]

• Fixed command encoding bugs:
  • CameraArmMode values now serialize correctly as "0" / "1" in Toggle* camera methods.
• Fixed PTZ behavior to match SecuritySpy spec:
  • Preset() now sends command 12-19.
  • PresetSave() now sends command 112-119.
  • PTZ capability bitmask updated so 16 = speed control, 32 = continuous movement, and added HasSpeed.
• Fixed nil-safety and refresh hardening:
  • GetJPEG(nil) no longer panics.
  • Refresh() now handles nil PTZ safely and missing schedule/override IDs without unsafe assumptions.
• Fixed transport behavior:
  • Post("++audio", ...) now correctly sets Content-Type: audio/g711-ulaw only for audio endpoint.
• Hardened event lifecycle and concurrency:
  • Reworked watch/stop lifecycle with cancellation + waitgroup, idempotent stop/start behavior.
  • Removed close-driven event channel shutdown race.
  • Added synchronization around runtime watcher fields.
  • Improved scanner reconnect loop and scanner error handling.
  • Made event parsing robust for short/optional-info lines and corrected trigger parsing precedence.
• Improved timeout/context behavior:
  • Get() / GetClient() now use bounded contexts.
  • Improved timeout fallback logic.
  • Added context-aware stream APIs:
    • StreamMJPGContext
    • StreamH264Context
    • StreamG711Context
  • Stream methods now use timeout-free clients for long-lived media streams.