feat: Add conducted emissions, near-field, filter design, immunity analyzers (#34-#37)

Wave 1 of prescan report excellence milestone:
- Conducted emissions analyzer with LISN model, SMPS harmonics, CISPR 25/FCC limits
- Near-field EMI probe modeling with magnetic/electric dipole fields
- EMI filter design with pi-filter, CMC, LC, ferrite bead insertion loss
- Immunity margin analysis with coupling paths, BCI, transfer impedance
- 164 new tests (1059 total), 4 new simulation plot types

Closes #34, closes #35, closes #36, closes #37

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: RFingAdam

src/mcp_pcb_emcopilot/analyzers/emc/__init__.py

@@ -7,6 +7,7 @@
 from .radiated_emissions import EmissionsAnalyzer, EmissionsResult
 from .grounding import GroundingAnalyzer, GroundingResult
 from .esd_assessment import ESDAnalyzer, ESDResult
+from .filter_design import FilterDesigner, FilterDesignResult
 
 __all__ = [
     "CurrentLoopAnalyzer",
@@ -19,4 +20,6 @@
     "GroundingResult",
     "ESDAnalyzer",
     "ESDResult",
+    "FilterDesigner",
+    "FilterDesignResult",
 ]