feat: deterministic CV-to-job match score endpoint

New JobCvMatchService: a pure, AI-free keyword-coverage scorer that
returns a stable, reproducible 0-100 match score plus matched/missing
keyword lists and per-CV-section coverage. Unlike candidate-fit (AI
narrative), it makes no model calls, so results are instant and
identical for identical inputs - the Jobscan-style differentiator.

- GET /api/jobapplications/{id}/match-score
- keywords = curated SkillTagger tags (high weight) + salient posting
  terms (title terms boosted); word-boundary matching avoids false hits
- section coverage shows where CV evidence is concentrated
- fix(SkillTagger): punctuation-tolerant C#/.NET patterns; the old \b
  boundaries silently missed 'C#,' and '.NET,' everywhere they are used
- 7 unit tests on the pure scorer; full backend suite green (104)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

JobTrackerApi/Services/JobImport/SkillTagger.cs

@@ -9,8 +9,10 @@ public static class SkillTagger
 {
     private static readonly (string Tag, Regex Pattern, int Weight)[] Patterns =
     {
-        ("C#", new Regex(@"\bC#\b|\bcsharp\b", RegexOptions.IgnoreCase | RegexOptions.Compiled), 6),
-        (".NET", new Regex(@"\b\.NET\b|\bASP\.NET\b|\bDOTNET\b|\bEntity Framework\b|\bEF Core\b", RegexOptions.IgnoreCase | RegexOptions.Compiled), 6),
+        // Symbol skills need punctuation-tolerant boundaries: \b fails next to '#'/'.'
+        // (both non-word chars), which previously left "C#," and ".NET," undetected.
+        ("C#", new Regex(@"(?<![A-Za-z0-9#])C#|\bc[-\s]?sharp\b", RegexOptions.IgnoreCase | RegexOptions.Compiled), 6),
+        (".NET", new Regex(@"(?<![A-Za-z0-9.])\.NET\b|\bASP\.NET\b|\bDOTNET\b|\bEntity Framework\b|\bEF Core\b", RegexOptions.IgnoreCase | RegexOptions.Compiled), 6),
         ("Python", new Regex(@"\bPython\b", RegexOptions.IgnoreCase | RegexOptions.Compiled), 6),
         ("Java", new Regex(@"\bJava\b", RegexOptions.IgnoreCase | RegexOptions.Compiled), 5),
         ("JavaScript", new Regex(@"\bJavaScript\b|\bJS\b", RegexOptions.IgnoreCase | RegexOptions.Compiled), 5),