security(plugins): fix critical security vulnerabilities in plugin system

WASM Runtime DoS Protection:
- Add fuel-based CPU limiting (10M operations max)
- Add epoch interruption support for timeout handling
- Implement ResourceLimiter with 16MB memory cap
- Add table/instance/memory limits
- Remove panic-prone Default impl for WasmRuntime

Path Traversal Prevention:
- Canonicalize all paths before access checks
- Resolve symlinks to prevent traversal via symlinks
- Validate paths stay within allowed boundaries
- Handle non-existent paths safely for write operations

Fail-Closed Security Model:
- Empty command allowlist now denies all commands
- Empty domain allowlist now denies all network access
- None allowed_domains denies network access
- Explicit opt-in required via '*' wildcard

SSRF Protection:
- Block localhost/loopback addresses (127.0.0.1, ::1, etc.)
- Block private IP ranges (10.x, 172.16-31.x, 192.168.x)
- Block link-local addresses (169.254.x.x)
- Block .local/.internal domain suffixes
- Block dangerous ports (SSH, databases, etc.)
- Allow only http/https protocols

Permission Hook Security:
- Document security implications of Allow decision
- Add requires_elevated_trust() method
- Add validate_for_third_party() method

Hook Priority Security:
- Reserve priorities 0-49 for system use
- Add SYSTEM_CRITICAL, SYSTEM, SYSTEM_HIGH constants
- Add PLUGIN_MIN (50), PLUGIN_HIGH (75) for third-party
- Add validate_for_plugin() method
- Deprecate HIGHEST/HIGH in favor of explicit names

SDK Safety Documentation:
- Add SAFETY comments to all unsafe FFI calls
- Document host contract assumptions

Author: echobt

Cargo.lock

@@ -19,6 +19,7 @@ toml = { workspace = true }
 
 # Error handling
 thiserror = { workspace = true }
+anyhow = { workspace = true }
 
 # Logging
 tracing = { workspace = true }