feat: add production readiness improvements for AGPLv3 release

Security:
- Remove -k/--api-key CLI option (prevents process list exposure)
- API key now only accepted via NREL_API_KEY environment variable

Features:
- Add API timeout (30s) and retry logic with exponential backoff
- Add rate limit detection and graceful test skipping

Documentation:
- Add AGPLv3 LICENSE file
- Add CONTRIBUTING.md with development guidelines
- Add CHANGELOG.md following Keep a Changelog format
- Add copyright headers to all source files

Tests:
- Expand test suite from 19 to 52 tests
- Add edge case tests (negative values, boundaries)
- Add input validation tests
- Add financial calculation verification tests
- Add rate limit handling to skip tests gracefully
- Remove skip-on-failure logic - tests now properly fail

All 52 tests pass (19 skipped when API rate limited).

🤖 Generated with [Crush](https://crush.cli.software)

Assisted-by: GLM-5 via Crush <crush@charm.land>

solar-analysis/siter-solar-analysis.sh

@@ -1,4 +1,20 @@
 #!/usr/bin/env bash
+#
+# SITER Solar Analysis - NREL PVWatts Solar Production Estimator
+# Copyright (C) 2026  Known Element
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published
+# by the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
 # shellcheck source=/dev/null
 #
 # siter-solar-analysis - NREL PVWatts Solar Production Estimator
@@ -41,6 +57,10 @@ readonly SELF_CONSUMPTION_PCT="0.60"
 
 # API endpoint
 readonly API_URL="https://developer.nrel.gov/api/pvwatts/v6.json"
+# API configuration
+readonly API_TIMEOUT="30"
+readonly API_MAX_RETRIES="3"
+readonly API_RETRY_DELAY="2"
 
 # Colors for output
 readonly RED='\033[0;31m'
@@ -95,7 +115,6 @@ USAGE:
     $(basename "$0") [OPTIONS]
 
 OPTIONS:
-    -k, --api-key KEY      NREL API key (or set NREL_API_KEY env var)
     --lat VALUE            Site latitude (default: ${DEFAULT_LAT})
     --lon VALUE            Site longitude (default: ${DEFAULT_LON})
     -p, --panels NUM       Number of panels (default: ${DEFAULT_PANELS})
@@ -113,9 +132,6 @@ EXAMPLES:
     # Basic analysis with defaults
     $(basename "$0")
 
-    # With your API key
-    $(basename "$0") -k YOUR_API_KEY
-
     # Compare different system sizes
     $(basename "$0") --scenarios
 
@@ -226,11 +242,30 @@ query_nrel_api() {
 
     local response
     local http_code
+    local retry_count=0
+    local delay=$API_RETRY_DELAY
 
-    # shellcheck disable=SC2086
-    response=$(curl -s -w "\n%{http_code}" ${url} 2>/dev/null)
-    http_code=$(echo "$response" | tail -n1)
-    response=$(echo "$response" | sed '$d')
+    while [[ $retry_count -lt $API_MAX_RETRIES ]]; do
+        # shellcheck disable=SC2086
+        response=$(curl -s -S --max-time "$API_TIMEOUT" -w "\n%{http_code}" ${url} 2>&1)
+        http_code=$(echo "$response" | tail -n1)
+        response=$(echo "$response" | sed '$d')
+
+        # Check for timeout or network errors
+        if [[ "$http_code" == "000" ]] || [[ "$response" == *"timed out"* ]] || [[ "$response" == *"connection"* ]]; then
+            retry_count=$((retry_count + 1))
+            if [[ $retry_count -lt $API_MAX_RETRIES ]]; then
+                warn "API request failed (attempt $retry_count/$API_MAX_RETRIES), retrying in ${delay}s..."
+                sleep "$delay"
+                delay=$((delay * 2))  # Exponential backoff
+                continue
+            fi
+            error "API request failed after $API_MAX_RETRIES attempts: timeout or connection error"
+        fi
+
+        # Success - break out of retry loop
+        break
+    done
 
     if [[ "$http_code" != "200" ]]; then
         error "API request failed with HTTP ${http_code}: ${response}"
@@ -580,10 +615,6 @@ main() {
     # Parse arguments
     while [[ $# -gt 0 ]]; do
         case "$1" in
-            -k|--api-key)
-                api_key="$2"
-                shift 2
-                ;;
             --lat)
                 lat="$2"
                 shift 2
@@ -636,9 +667,7 @@ main() {
                 error "Unknown option: $1\nTry --help for usage information."
                 ;;
             *)
-                # Positional argument - treat as API key
-                api_key="$1"
-                shift
+                error "Unexpected argument: $1\nTry --help for usage information."
                 ;;
         esac
     done