Add cover letter format, llms.txt enhancements & Phantom/Solflare applications

- CLAUDE.md: Add cover letter RST format guide
- Makefile: Use cover-letter.style for PDF generation
- lib/generate_llms_txt.py: Add contact, payment, software, ML expertise & commission sections
- New cover letters: Phantom Backend (Money Movement), Solflare Backend Developer
- cover-letter.style: rst2pdf styling for clean PDF output

CLAUDE.md

@@ -148,6 +148,46 @@ Git operations can be destructive to uncommitted work. Always preserve user's wo
 
 **NEVER include phone number in JSONResume files** - they're public, use email only.
 
+## COVER LETTER FORMAT
+
+**Location:** `content/pages/cover-letters/`
+
+**Naming:** `YYYY-MM-DD-company-role-russell-ballestrini.rst`
+
+**Generate PDF:** `make cover-letters` (uses rst2pdf with style file)
+
+**RST structure (match resume format):**
+```rst
+Russell Ballestrini
+===================
+
+.. class:: center
+
+**Role Title | Company Name**
+
+.. class:: center
+
+russell@unturf.com | `russell.ballestrini.net <https://russell.ballestrini.net>`_ | `GitHub <https://github.com/russellballestrini>`_
+
+----
+
+To the [Company] team:
+
+[Body of letter...]
+
+|
+
+Russell Ballestrini
+```
+
+**Key formatting rules:**
+- Name as RST title (=== underline)
+- Use `.. class:: center` for role & contact info
+- Horizontal rule (----) separates header from body
+- No Pelican metadata in PDF-only letters (or use RST comments to hide)
+- Use `|` for vertical spacing before signature
+- Links use RST inline syntax: ```link text <URL>`_``
+
 ## DATE HANDLING FOR NEW CONTENT
 
 **CRITICAL: ALWAYS check the current date BEFORE creating ANY new documents**