Add dissertation PDFs and update spreadsheet with images/links

Dissertations added:
- Owen LLW (2021): Modeling the fast-timescale network dynamics that underlie complex thought
  - Image: timecorr.png
  - PDF: data/pdfs/owen_dissertation.pdf

- Ziman K (2022): Attending and remembering the external world
  - Image: ZimaEtAl19-34.png (attention timescale paper)
  - PDF: data/pdfs/ziman_dissertation.pdf

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: jeremymanning

data/pdfs/owen_dissertation.pdf

@@ -468,17 +468,17 @@ <h4><a href="http://caligari.dartmouth.edu/~jmanning/pubs/magellan_dissertation.
                 </div>
 
                 <div class="publication-card">
-                    <img src="" alt="Publication thumbnail">
+                    <img src="images/publications/timecorr.png" alt="Publication thumbnail">
                     <div>
-                        <h4>Modeling the fast-timescale network dynamics that underlie complex thought</h4>
+                        <h4><a href="data/pdfs/owen_dissertation.pdf" target="_blank">Modeling the fast-timescale network dynamics that underlie complex thought</a></h4>
                         <p>Owen LLW (2021) Modeling the fast-timescale network dynamics that underlie complex thought. <em>Doctoral dissertation: Dartmouth College</em>, Hanover, NH.</p>
                     </div>
                 </div>
 
                 <div class="publication-card">
-                    <img src="" alt="Publication thumbnail">
+                    <img src="images/publications/ZimaEtAl19-34.png" alt="Publication thumbnail">
                     <div>
-                        <h4>Attending and remembering the external world</h4>
+                        <h4><a href="data/pdfs/ziman_dissertation.pdf" target="_blank">Attending and remembering the external world</a></h4>
                         <p>Ziman K (2022) Attending and remembering the external world. <em>Doctoral dissertation: Dartmouth College</em>, Hanover, NH.</p>
                     </div>
                 </div>