Add pi3b hardware tier and resource guards for condo Pi deployment

- Add pi3b tier (700MB RAM limit, 8 passive/2 active modules, no bettercap/mitmproxy)
- Update detect_hardware_tier() to detect Raspberry Pi 3B by model string and BCM2837
- Add pi3b section to hardware_tiers.yaml
- Add systemd MemoryMax/CPUQuota/OOMScoreAdj to all three service files
- Fix bigbrother-watchdog.service ExecStart (was calling non-existent ResourceMonitor().run())
- Add scripts/run_watchdog.py as standalone health monitor daemon

config/hardware_tiers.yaml

@@ -23,6 +23,27 @@ opi_zero3:
   wifi_attacks: true                # Built-in WiFi 5 supports evil twin
   inline_bridge: true               # Via USB Ethernet adapter
 
+# ---------------------------------------------------------------------------
+# Raspberry Pi 3B — Condo / Secondary Implant
+# BCM2837B0, 4x Cortex-A53 @ 1.2GHz, WiFi 4 + BT 4.2, 1x 100M Ethernet
+# 1GB RAM — passive sniffing + limited active capability
+# OS: Ubuntu 24.04 LTS (arm64)
+# ---------------------------------------------------------------------------
+pi3b:
+  max_passive: 8                    # 8 passive modules (RAM-limited)
+  max_active: 2                     # Minimal active capability
+  max_ram_mb: 700                   # 900MB total - ~200MB OS overhead
+  zstd_level: 3                     # Fast compression (CPU-limited)
+  kdf: "pbkdf2"                     # argon2id too expensive for 1GB
+  mitmproxy: false                  # Too RAM-heavy
+  lkm: false                        # No kernel headers
+  cellular: false                   # No USB header
+  overlayfs_mb: 64                  # Small tmpfs overlay
+  thermal_warning: 60               # Celsius — Pi 3B runs warm
+  thermal_shed: 75                  # Shed modules at this temp
+  wifi_attacks: false               # Single wlan0 = uplink, can't spare for monitor
+  inline_bridge: false              # eth0 is down at condo
+
 # ---------------------------------------------------------------------------
 # Raspberry Pi Zero 2W — Jumpbox / Beacon
 # BCM2710A1, 4x Cortex-A53 @ 1.0GHz, WiFi 4, no Ethernet (USB adapter)