Initial import of STM32 IoT sensor node

.gitignore

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+# Keil build output
+/project/Objects/
+/project/Listings/
+/project/DebugConfig/
+/project/EventRecorderStub.scvd
+*.o
+*.obj
+*.axf
+*.elf
+*.hex
+*.bin
+*.crf
+*.d
+*.dep
+*.lnp
+*.map
+*.lst
+*.build_log.htm
+
+# Keil per-user settings and backups
+*.uvopt
+*.uvoptx
+*.uvgui.*
+*.uvguix.*
+*.uvproj.bak
+*.uvprojx.bak
+*.uvoptx.bak
+
+# Local editor and assistant settings
+.vscode/
+.idea/
+.claude/
+.codex/
+.agents/
+
+# Private device/network configuration
+/user/network_config.h
+.env
+.env.*
+!.env.example
+
+# Temporary files
+*.log
+*.lock
+*.tmp
+*.bak
+*~
+.DS_Store
+Thumbs.db
+Desktop.ini