Add generic ADAU1701 parameter access (GET/PUT /api/dsp/param)

New core::IDsp::writeRawParam(address, value) safeloads any named
Parameter RAM cell in the compiled SigmaStudio program (74 cells: mixer/
Beep1/PEQ coefficients/limiter thresholds/etc — the same set SigmaStudio's
own Remote Connection, components/net/SigmaStudioTcpServer, already has
full access to). Value is a plain SigmaStudio floating coefficient,
converted to ADAU 8.23 fixpoint via the existing core::floatToFixpoint823.

Adau1701ParamTable.hpp holds the name->address table extracted from
Firmware/ADAU1701-Firmware/DigiRadio_IC_1_PARAM.h; core::DspParamJson
handles the wire format without core/ depending on the adau1701 driver
(net/SetupWebServer.cpp bridges the two, consistent with how other
JSON DTOs are supplied their data by the net layer).

GET /api/dsp/params lists every cell (name + address) for discovery.
PUT /api/dsp/param {"name":...,"value":...} writes one. Deliberately no
domain validation, matching the trust level already implied by the
existing SigmaStudio TCP bridge being reachable on the same network.
HTTP routes were registered in the SetupWebServer.cpp change committed
alongside the FM band scan feature (3a10ed7).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0178rASQ6ZETPMUamvpoR2KR

Software/components/services/audio/include/audio/AudioService.hpp

@@ -208,6 +208,22 @@ public:
     [[nodiscard]] std::expected<void, core::DspError> setBeepEnabled(
         bool enabled);
 
+    /**
+     * @brief    writeRawParam — safeload any named ADAU1701 Parameter RAM cell.
+     *
+     * @dname    writeRawParam
+     * @param    address  Parameter RAM address.
+     * @param    value    Coefficient in the SigmaStudio floating convention.
+     * @return   Ok on success, or DspError.
+     * @pubstate live-only: not part of AudioProfile, never persisted, does
+     *           not touch profile_. No domain validation.
+     *
+     * @author   Michele Bigi
+     * @date     2026-08-18
+     */
+    [[nodiscard]] std::expected<void, core::DspError> writeRawParam(
+        unsigned address, float value);
+
 private:
     [[nodiscard]] std::expected<void, core::StoreError> persistProfile() const;
 

Software/components/services/audio/src/AudioService.cpp

@@ -193,4 +193,10 @@ std::expected<void, core::DspError> AudioService::setBeepEnabled(bool enabled)
     return dsp_.setBeepEnabled(enabled);
 }
 
+std::expected<void, core::DspError> AudioService::writeRawParam(
+    unsigned address, float value)
+{
+    return dsp_.writeRawParam(address, value);
+}
+
 } // namespace audio