feat: integrate LDPC decoder into Caravel wrapper

- Copy ldpc_decoder_core.sv and wishbone_interface.sv from standalone RTL
- Create Caravel-adapted ldpc_decoder_top.sv with USE_POWER_PINS,
  32-bit address (lower 8 bits passed through), and wb_sel_i port
- Replace user_proj_example in user_project_wrapper.v with LDPC decoder
  instantiation, active-high to active-low reset inversion, and tie-offs
  for unused outputs (la_data_out, io_out, io_oeb, user_irq[2:1])
- Update includes.rtl.caravel_user_project with LDPC RTL file list
- Fix invalid hex literal in VERSION_ID (0xLD -> 0x1D)

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

verilog/includes/includes.rtl.caravel_user_project

@@ -14,7 +14,8 @@
 # SPDX-License-Identifier: Apache-2.0
 
 # Caravel user project includes
--v $(USER_PROJECT_VERILOG)/rtl/user_project_wrapper.v	     
--v $(USER_PROJECT_VERILOG)/rtl/user_proj_example.v
-
- 
+-v $(USER_PROJECT_VERILOG)/rtl/defines.v
+-v $(USER_PROJECT_VERILOG)/rtl/user_project_wrapper.v
+-v $(USER_PROJECT_VERILOG)/rtl/ldpc_decoder_top.sv
+-v $(USER_PROJECT_VERILOG)/rtl/ldpc_decoder_core.sv
+-v $(USER_PROJECT_VERILOG)/rtl/wishbone_interface.sv