chore: Add clippy lints and fix violations

[joshuaclayton]

New lints:

• unwrap_used: complements existing expect_used; prevents .unwrap() in
  library code
• wildcard_enum_match_arm: complements exhaustive_enums; forces explicit
  variant handling instead of _ catch-alls
• missing_errors_doc: enforces # Errors sections on public Result-returning fns
• missing_panics_doc: enforces # Panics sections where applicable
• redundant_else: removes else after blocks that already return/break

Fixes:

• Add unwrap_used to test module expect lists (alongside existing expect_used)
• Expand wildcard match arms in jwks.rs to list variants explicitly
• Replace wildcard match in pages.rs error formatting with if-let
• Replace match/panic patterns in page tests with assert!(matches!(...))

Co-Authored-By: Claude Opus 4.6 (1M context) noreply@anthropic.com