feat: create a blobdecoder tool (#2628)

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## Overview

I was debugging and whipped up a blob decoder, we can throw it up
somewhere if we want. I found it useful, someone else may as well

---------

Co-authored-by: Julien Robert <[email protected]>

Author: tac0turtle

docs/guides/da/blob-decoder.md

@@ -0,0 +1,152 @@
+# Blob Decoder Tool
+
+The blob decoder is a utility tool for decoding and inspecting blobs from Celestia (DA) layers. It provides both a web interface and API for decoding blob data into human-readable format.
+
+## Overview
+
+The blob decoder helps developers and operators inspect the contents of blobs submitted to DA layers. It can decode:
+- Raw blob data (hex or base64 encoded)
+- Block data structures
+- Transaction payloads
+- Protobuf-encoded messages
+
+## Usage
+
+### Starting the Server
+
+```bash
+# Run with default port (8080)
+go run tools/blob-decoder/main.go
+```
+
+The server will start and display:
+- Web interface URL: `http://localhost:8080`
+- API endpoint: `http://localhost:8080/api/decode`
+
+### Web Interface
+
+1. Open your browser to `http://localhost:8080`
+2. Paste your blob data in the input field
+3. Select the encoding format (hex or base64)
+4. Click "Decode" to see the parsed output
+
+### API Usage
+
+The decoder provides a REST API for programmatic access:
+
+```bash
+# Decode hex-encoded blob
+curl -X POST http://localhost:8080/api/decode \
+  -H "Content-Type: application/json" \
+  -d '{
+    "data": "0x1234abcd...",
+    "encoding": "hex"
+  }'
+
+# Decode base64-encoded blob
+curl -X POST http://localhost:8080/api/decode \
+  -H "Content-Type: application/json" \
+  -d '{
+    "data": "SGVsbG8gV29ybGQ=",
+    "encoding": "base64"
+  }'
+```
+
+#### API Request Format
+
+```json
+{
+  "data": "string",      // The encoded blob data
+  "encoding": "string"   // Either "hex" or "base64"
+}
+```
+
+#### API Response Format
+
+```json
+{
+  "success": true,
+  "decoded": {
+    // Decoded data structure
+  },
+  "error": "string"  // Only present if success is false
+}
+```
+
+## Supported Data Types
+
+### Block Data
+
+The decoder can parse ev-node block structures:
+- Block height
+- Timestamp
+- Parent hash
+- Transaction list
+- Validator information
+- Data commitments
+
+### Transaction Data
+
+Decodes individual transactions including:
+- Transaction type
+- Sender/receiver addresses
+- Value/amount
+- Gas parameters
+- Payload data
+
+### Protobuf Messages
+
+Automatically detects and decodes protobuf-encoded messages used in ev-node:
+- Block headers
+- Transaction batches
+- State updates
+- DA commitments
+
+## Examples
+
+### Decoding a Block Blob
+
+```bash
+# Example block blob (hex encoded)
+curl -X POST http://localhost:8080/api/decode \
+  -H "Content-Type: application/json" \
+  -d '{
+    "data": "0a2408011220...",
+    "encoding": "hex"
+  }'
+```
+
+Response:
+```json
+{
+  "success": true,
+  "decoded": {
+    "height": 100,
+    "timestamp": "2024-01-15T10:30:00Z",
+    "parentHash": "0xabc123...",
+    "transactions": [
+      {
+        "type": "transfer",
+        "from": "0x123...",
+        "to": "0x456...",
+        "value": "1000000000000000000"
+      }
+    ]
+  }
+}
+```
+
+### Decoding DA Commitment
+
+```bash
+curl -X POST http://localhost:8080/api/decode \
+  -H "Content-Type: application/json" \
+  -d '{
+    "data": "eyJjb21taXRtZW50IjogIi4uLiJ9",
+    "encoding": "base64"
+  }'
+```
+
+### Celestia
+
+For Celestia blobs, you can decode namespace data and payment information from [celenium](https://celenium.io/namespaces).